Broadening the Tax Base

Broadening the Tax Base: Cost-Benefit Analysis of Proposed Reforms

The proposal seeks to broaden the U.S. federal tax base through a suite of measures: a new carbon dividend (carbon tax with rebate), a financial transaction tax (FTT), and closing loopholes for carried interest, offshore income, and unrealized capital gains. Additionally, it calls for narrowing the $540+ billion annual tax gap via enhanced enforcement and technology. This analysis examines the fiscal impacts over a 5–15 year horizon, including projected net revenue gains, administrative costs, and enforcement efficiency. It also compares these measures to maintaining the status quo or using non-tax alternatives (like borrowing or spending cuts), and draws on international case studies (e.g. EU’s FTT, Canada’s carbon dividend, OECD transparency efforts) for context. The goal is to provide policymakers a detailed cost-benefit perspective, using real-dollar estimates and structured comparisons to baseline scenarios.

Projected Revenue Gains from Proposed Measures

Carbon Dividend (Carbon Tax) – Implementing a federal carbon tax with proceeds rebated to citizens (“carbon dividend”) could significantly broaden the tax base and raise substantial gross revenue. For example, the Congressional Budget Office (CBO) analyzed a $25 per ton CO₂ tax (rising 5% above inflation annually): it would generate about $865 billion over 10 years (2023–2032), net of interactions with other taxes. Even a smaller or slower-ramping carbon tax yields hundreds of billions (e.g. ~$770 billion over 10 years if rising 2% plus inflation).These figures represent gross revenue that would be collected; under a carbon dividend design, most of this money is returned to households as rebates. Canada’s federal carbon pricing regime, for instance, rebates ~90% of carbon tax revenues to households to offset higher energy costs. In Canada’s case, the policy has been nearly revenue-neutral for the government (funds flow back to citizens), yet it still contributes to emissions reductions and most households (around 80%) come out net-positive after the rebate.For the U.S., a similar approach could return money to taxpayers while still leveraging the behavioral benefits of a carbon tax (pricing carbon externalities). Net fiscal impact: If 100% of revenues are rebated, the direct deficit reduction is zero; however, policymakers could opt to retain a portion of the revenue for deficit reduction or other programs. Even with full dividends, there are indirect fiscal benefits: lower climate-related damages long-term (which can affect the budget) and potentially avoiding costlier regulation. In sum, a carbon tax/dividend would broaden the tax base (new revenue stream from emissions) and could gross tens of billions per year, but its net contribution to the treasury depends on the rebate structure. Administrative costs for a carbon tax are moderate – it can piggyback on existing fuel excise tax collection systems – and Canada’s experience shows it’s feasible to implement nationally. The cost-benefit tradeoff also includes environmental gains: by 2032, U.S. energy-related emissions might be ~11% lower than under current policy with a moderate carbon tax, reducing future economic damage from climate change, an important ancillary benefit beyond fiscal metrics.

Financial Transaction Tax (FTT) – A small tax on trades of stocks, bonds, or derivatives would tap into a very broad base of financial activity. According to Joint Committee on Taxation (JCT) and CBO estimates, a 0.1% FTT on all securities could raise roughly $777 billion over 10 years. That equates to about $75–80 billion per year in federal revenue – a sizable new source.The revenue yield, however, is sensitive to market reactions: if trading volumes significantly decline or migrate to untaxed venues, actual revenues could be lower. Experiences abroad show mixed results. For instance, the United Kingdom’s stamp duty on stock trades (0.5%) has existed for decades and reliably raised on the order of £3–5 billion annually (around 0.3–0.4% of GDP in strong market years). France and Italy implemented narrower FTTs (on stock purchases of large companies) which raise more modest amounts (e.g. France’s 0.3% FTT brings in on the order of a few billion euros per year). The EU as a whole has debated an FTT to avoid intra-Europe trading shifts, with an agreement among some countries to implement a harmonized FTT, though full EU-wide adoption has faced hurdles. Cost-benefit considerations: An FTT would directly raise revenue primarily from financial market participants – effectively a very progressive source (since wealthy investors and institutions conduct the most trading). It could also dampen excessively high-frequency trading, potentially reducing volatility. On the cost side, critics argue it may widen bid-ask spreads and raise the cost of capital marginally, and if set too high, could push trading offshore. However, by setting the rate low (e.g. 0.1% or less) and designing it broadly (to minimize easy avoidance), these downsides can be mitigated. The administrative cost of collecting an FTT is relatively low because it can be integrated into clearing and settlement systems (modern technology makes automatic collection feasible.). In sum, an FTT offers a large fiscal upside (~$700+ billion/decade) with a mostly manageable impact on markets if coordinated and kept at a low rate, as evidenced by the UK and other countries’ long-running transaction taxes.

Carried Interest Loophole – Currently, private equity and hedge fund managers often treat their performance fees (“carried interest”) as long-term capital gains, taxed at about 20%, rather than as ordinary income taxed up to 37%. Closing this loophole (i.e. taxing carried interest as regular income) would raise only a small amount of revenue relative to other proposals – roughly $13–14 billion over 10 years per CBO estimates. That’s on the order of $1–2 billion per year, because the universe of affected taxpayers is small (albeit very wealthy) and the volume of carried interest income is limited. While modest in fiscal terms (just a few hundredths of a percent of federal revenue), closing this loophole is often justified on grounds of fairness: it would equalize tax rates between fund managers’ income and wages/salaries earned by other workers The administrative cost and complexity of this reform are minimal – it’s a simple change in tax treatment. Benefit-cost summary: Net revenue gain of ~$1.3B/year, virtually no implementation cost, and an improvement in tax equity (eliminating a tax preference that primarily benefits ultra-high-income individuals). The effect on investment levels or the economy would likely be negligible (as the capital backing private equity funds already seeks high returns and the fee tax change is a second-order consideration). Most advanced economies do not give such generous treatment to fund managers; ending it would align the U.S. more with international norms on capital income taxation. Overall, this is a low-hanging fruit policy: politically symbolic and equitable, albeit fiscally minor.

Offshore Corporate Income and Tax Havens – Multinational companies often shift profits to low-tax jurisdictions, eroding the U.S. tax base. The proposal to end loopholes for offshore income includes measures like raising the global minimum tax on U.S. multinationals’ foreign earnings, eliminating the tax exemption for the first 10% return on tangible assets abroad, and tightening rules so profits are taxed per country rather than blended, among others. The potential revenue impact is very large. Senate legislation scored by JCT indicates that stopping the use of offshore tax havens by corporations could raise over $1 trillion in revenue over 10 years.. This figure likely assumes a combination of reforms – for example, increasing the tax rate on global intangible low-tax income (GILTI) to 21% (from the current ~10.5%), aligning with the new OECD-led 15% global minimum tax, and closing gaps that allow profit shifting. President Biden’s recent budget proposals in this area illustrate the magnitude: strengthening global minimum tax rules was projected to raise about $374 billion/decade, adopting a worldwide “undertaxed profits” rule another $136 billion and repealing the 10% tangible asset exemption (part of the 2017 law) would add more. Cumulatively, international reform efforts could easily top half a trillion over 10 years, and aggressive crackdowns approach $1T when combined with a higher corporate rate. International context: The OECD’s Base Erosion and Profit Shifting (BEPS) initiative and the 2021 global agreement on a 15% minimum corporate tax indicate broad support for curbing profit shifting. Many U.S. allies (UK, EU members, etc.) are implementing the global minimum tax in 2024–2025, which means U.S. multinationals will face those taxes even if the U.S. doesn’t act – so it makes sense for the U.S. to collect that revenue instead of foreign governments. The benefit of closing offshore loopholes is not only the direct revenue gained, but also improved competitiveness and fairness for purely domestic companies (who currently may be at a tax disadvantage). Costs/implementation: Corporations may argue higher taxes reduce investment, but by coordinating globally, the playing field is leveled and the impact on investment locations is minimized. The administrative effort involves complex international tax rules, but the IRS already administers GILTI; reforms would build on existing mechanisms. Moreover, tax transparency improvements globally make enforcement easier: under the OECD’s Common Reporting Standard, tax authorities now automatically exchange information on millions of accounts – in 2022, information on 123 million financial accounts (worth €12 trillion) was shared among countries. This data trove helps identify offshore earnings and assets. Already, over €114 billion in additional tax revenue worldwide has been recovered through voluntary disclosures and audits spurred by these transparency initiatives. In summary, cracking down on offshore tax avoidance offers one of the highest fiscal upsides of any proposal (hundreds of billions to ~$1T over a decade), with growing international momentum to back it and modern data tools to enforce it. The trade-off is tighter rules for multinationals – effectively asking them to pay closer to the full 21% U.S. rate on their global profits, which many major companies can clearly afford given record profits and the modest effective rates many paid under prior law (often under 10–15%).

Unrealized Capital Gains (“Billionaires’ Tax” and Step-Up Basis) – Perhaps the most novel (and challenging) piece is taxing unrealized capital gains, which addresses the fact that the ultra-wealthy can accrue vast wealth growth without ever “realizing” income for tax purposes. Two approaches are often discussed: (1) End stepped-up basis at death, so that unrealized gains are taxed when assets transfer to heirs; (2) Annual wealth tax or minimum income tax on unrealized gains for extremely rich households. The proposal generally aims to end the “loophole” that currently allows untaxed gains to escape taxation entirely if held until death. The revenue potential is significant. CBO analysis shows that simply taxing capital gains at death (rather than forgiving the tax via step-up) could raise on the order of $500+ billion over 10 years (if applied broadly). Even a more limited reform – carryover basis (heirs pay gain when they sell) – was estimated at about $110 billion/decade, while taxing gains at death immediately could be around $200 billion/decade by some estimates assuming exemptions for small estates. President Biden’s “Billionaire Minimum Income Tax” proposal is instructive: it would require households worth over $100 million to pay at least 25% tax on their total income, including unrealized gains. This was projected to raise about $503 billion over 10 years, targeting only the top 0.01% of wealth holders. In effect, that policy is a periodic tax on unrealized gains (with deferral and smoothing mechanisms) for the richest Americans. These numbers indicate that taxing unrealized gains (whether at death or periodically for the ultra-rich) could yield hundreds of billions in the medium term – roughly $30–50 billion per year once fully implemented. Qualitative benefits: This would close a major tax avoidance strategy used by billionaires – “buy, borrow, die” – wherein they never sell assets but borrow against them, then pass them to heirs tax-free. It would also enhance fairness, ensuring the very wealthy pay tax on income that currently goes untaxed, thereby reducing inequality. Administrative and economic challenges: Implementing a tax on unrealized gains is the most complex of the proposals. It requires annual or at-death valuation of assets, which can be hard for illiquid assets like private businesses or real estate. However, mechanisms exist (e.g. allowing payment of tax over several years for illiquid assets, or deferring tax until actual sale with an interest charge, etc.). Countries like Canada tax capital gains at death (with some exceptions), and many OECD countries have inheritance or wealth taxes, indicating it’s feasible to tax large accumulations of wealth. The U.S. already has an estate tax (though with a high exemption); taxing unrealized gains at death could piggyback on estate tax administration. Care would be needed to prevent double taxation by crediting any estate tax paid. Economically, a moderate tax on unrealized gains for the super-rich is unlikely to deter productive investment – those individuals would remain enormously wealthy post-tax. It may, however, discourage locking wealth in low-basis assets purely for tax reasons and could unlock more economic activity (the current step-up rule encourages holding assets until death rather than selling or reinvesting). In summary, ending the unrealized gains loophole could raise on the order of $300–500 billion/decade depending on design, improving tax justice at the cost of added complexity in the tax code. Policymakers would need to invest in valuation expertise and perhaps phasing rules, but the payoff is substantial revenue from those most able to contribute.

Closing the Tax Gap (Enforcement) – The “tax gap” – the difference between taxes owed under the law and taxes actually paid – is estimated at around $540 billion per year gross (2017–2019 average), or about $470 billion/year net after late payments and enforcement. Closing this gap (even partially) represents a major fiscal opportunity. The proposal envisions using advanced enforcement and technology to recoup unpaid taxes. Recent U.S. policy moves provide insight: The Inflation Reduction Act of 2022 invested roughly $80 billion in the IRS over 10 years to bolster enforcement, technology, and taxpayer services. The CBO estimated this would yield about $200 billion in additional revenue over a decade– a net deficit reduction around $120 billion after the cost of investment. That implies an average ROI of 2.5:1 for the marginal enforcement dollars. Treasury and the White House anticipated even higher returns (up to $400 billion net over a decade), but CBO was more conservative Importantly, those estimates account for diminishing returns – initial audits yield high ROI (the IRS historically brings in about $7-$9 per $1 on enforcement on average), but scaling up requires hiring and training agents, upgrading IT, and may be less efficient at the margins. The proposal’s aspiration to close the $540B annual gap entirely is ambitious; in practice, no country collects 100% of taxes owed. However, even shrinking the gap by 10-20% would yield huge revenue – on the order of $50–100 billion per year in sustained collections. With advanced data analytics, AI, and better information reporting, these gains are plausible. For example, a Stanford study finds that auditing complex partnerships (a known tax avoidance vehicle) can return $20 for every $1 spent – far higher than typical enforcement ROI Targeting such high-noncompliance areas (like pass-through businesses, offshore evasion, cryptocurrency transactions, etc.) using modern technology could significantly boost effective collections. The cost side of enforcement is the budget for the IRS (hiring skilled auditors, improving IT systems for cross-checking data, etc.) and potential increased compliance burden on taxpayers. The proposal’s focus on technology suggests using data matching, machine learning, and better information flows to spot evasion with less need for brute-force audits. Expanded third-party reporting (for instance, banks reporting aggregate account flows, or cryptocurrency exchanges reporting transactions) can automate compliance. Internationally, OECD tax transparency efforts (like automatic bank account info exchange) have made it much harder to hide income – as noted, tax authorities exchanged info on accounts worth €12 trillion in 2022, leading to voluntary disclosures that brought in over €100 billion in back taxes and penalties globally. The U.S. benefits from some of these efforts (via FATCA and bilateral agreements) and could benefit more by joining broader data-sharing. In sum, closing the tax gap is one of the most cost-effective fiscal measures: it raises revenue without raising tax rates, simply by enforcing existing laws. A well-resourced, modernized IRS would improve collection and also enhance fairness (honest taxpayers won’t feel like evaders are getting a free ride). The main caveat is that enforcement must respect privacy and avoid overly harsh tactics on small taxpayers; the emphasis should be on big-dollar evasion and high-tech solutions. With tens of billions at stake annually, the net benefit is clearly positive. For perspective, the CBO projects that over 2025–2035, net interest on the national debt will total $13.8 trillion; recouping even a quarter of the annual tax gap over the next decade (say $1.3 trillion total) would cover a tenth of that interest burden – a meaningful dent achieved just by improving efficiency.

Administrative and Implementation Considerations

Implementing this comprehensive tax-base-broadening agenda would entail upfront administrative efforts, but each component is grounded in precedent either domestically or internationally:

• Carbon Tax/Dividend: The IRS (or Treasury) would need to collect the tax from fuel suppliers and large emitters – a system similar to existing excise taxes on gasoline, coal, etc. Many emissions are already tracked, so it’s mainly a matter of setting up the tax rates and monitoring compliance. Returning the revenue as dividends means an outlay system (likely through the IRS via tax returns or direct payments). Canada’s experience shows this is manageable – they disburse climate rebates quarterly to households. Administrative costs are relatively small compared to the revenue; Canada’s federal system uses an online portal and the tax filing process for distribution. The key implementation challenge is coordination with states and industries on measuring emissions. A potential need is a border carbon adjustment mechanism to tax imports from countries without similar carbon pricing, to protect U.S. manufacturers – this adds complexity but is being explored internationally (the EU is phasing in a carbon border adjustment). Overall, the carbon tax’s machinery is straightforward as a fiscal instrument, and its success will be judged by emissions reductions and public acceptance of the rebates.

• Financial Transaction Tax: This would be collected automatically by exchanges and clearinghouses on each trade. The U.S. Securities and Exchange Commission already collects a tiny fee (Section 31 fee) on trades (to fund itself), which proves the concept. Scaling that up to a broader FTT is technically simple once legislated. The bigger issue is ensuring trades can’t just migrate to avoid the tax. To mitigate avoidance, the tax should cover all trades involving U.S. exchanges or U.S. parties (as proposed). Enforcement would involve monitoring compliance by broker-dealers – again, something regulators already do. The administrative cost is low since it’s largely piggybacking on electronic transaction infrastructure. One consideration is coordinating with major financial centers (London, EU, etc.): if they also have FTTs (many EU countries do, and the EU has discussed a coordinated FTT), the risk of capital flight lessens. Even absent perfect coordination, the broad base of U.S. markets (and minimal tax rate) means most investors would likely stay. In implementation, regulators would watch for any liquidity impacts or market structure changes (for example, could high-frequency trading volume drop? Yes, likely by design; could that harm market liquidity? Evidence from places like France suggests only a modest impact for a low-rate FTT). Policymakers might adjust specifics (exempt market makers or pension funds, etc., though exemptions also shrink the base). In summary, administratively an FTT is one of the easier taxes to collect; the main implementation “cost” is ensuring the financial sector adapts smoothly.

• Closing Loopholes (Carried Interest, etc.): These are primarily legal changes with minimal administrative burden. Ending carried interest preferences is simply rewriting tax code sections – fund managers would receive a Form K-1 (or 1099) showing that income as non-capital-gain compensation. The IRS would issue guidance, but private equity and hedge funds already track these allocations, so compliance is straightforward. Similarly, changing rules for offshore income (GILTI and related international tax rules) involves tax code changes and Treasury regulations. Corporations would have to adjust their tax planning and reporting, but large multinationals already comply with detailed GILTI reporting. The IRS may need to develop regulations for the new global minimum tax calculations (on a per-country basis) and coordinate information with other countries. The OECD framework actually aids this – there are common templates for country-by-country reporting of profits and taxes paid, which the IRS can use to verify companies’ calculations. One administrative challenge: if the U.S. taxes foreign subsidiaries more, there’s a risk of increased tax credit claims (to avoid double taxation). But careful design (like disallowing cross-crediting between high-tax and low-tax countries) in line with OECD norms will handle this. Taxing unrealized gains is the most administratively complex: it may require annual appraisals for certain assets or a tracking of basis over generations. For a billionaire minimum tax, the IRS would need to collect comprehensive information on ultra-wealthy taxpayers’ asset portfolios. This could be aided by third-party reporting for financial assets, but valuing privately held business interests might need periodic expert appraisal. Those are not trivial tasks, but the number of affected taxpayers is very small (a few thousand households). The IRS could create a specialized high-wealth examination unit (something it is already ramping up) to handle this. The estate tax system could be leveraged for at-death gain taxation: estate tax returns already list assets and values, so adding a capital gains schedule for the decedent’s assets is feasible (Canada effectively does this in its tax system). Transitional rules would be needed (e.g. for existing unrealized gains if applying a new tax at death). In terms of cost, the IRS might need additional estate/gift tax attorneys and valuation experts – a relatively small investment relative to the revenue at stake.

• IRS Modernization and Technology: A linchpin of closing the tax gap is giving the IRS the tools to detect evasion. This means upgraded IT systems that can cross-match data (for example, matching bank account info, 1099-K reports from payment apps, cryptocurrency exchange reports, foreign account data, etc., with tax returns). The $80 billion funding boost provided in 2022 is intended to do exactly this. The implementation will occur over several years: hiring new revenue agents, data scientists, and customer service reps; modernizing decades-old software; and expanding data analytics. Some of that is already underway – the IRS in 2023 launched a new Strategic Operating Plan focusing on data and AI to select audit targets more effectively. International cooperation is another facet: the IRS will increasingly utilize data from the OECD’s information exchanges (FATCA already gives the U.S. data on Americans’ accounts abroad). The risks of heavy enforcement can be political – there were concerns (often overstated) that an “army of IRS agents” would audit middle-class folks. In reality, the IRS will likely concentrate on high-end noncompliance (where the big dollars are). The agency will also use tech to make honest compliance easier (pre-filled returns for simple wages, better online services), which indirectly boosts revenue by reducing errors. Enforcement efficiency is about smart targeting. As cited, certain complex partnership structures have extremely low audit rates now – improving that can bring large returns. Another example: offshore evasion by individuals (e.g. hidden accounts) can be tackled with data-mining the troves of info now available. The cost-benefit here is stark – every additional IRS dollar has a high expected return (even at CBO’s cautious estimate, $2.5:$1crfb.org, and potentially much higher). Thus, the implementation question is mostly about phasing and oversight: ensuring the IRS money is spent effectively on the most up-to-date systems and skilled personnel. By year 5, we would expect audit and collection rates on top earners and corporations to rise, voluntary compliance to improve (if people know detection is likely), and the tax gap to shrink measurably.

International Case Studies and Comparisons

Each element of this proposal has analogues or lessons from abroad:

• Carbon Taxes/Dividends: Besides Canada, numerous countries (in Europe, Asia, and Latin America) have carbon taxes or emissions trading systems that raise revenue. For example, Sweden has one of the highest carbon taxes (over $130/ton) and uses the revenue for general government funds and environmental initiatives, while Switzerland and Canada return a large share to citizens as a dividend. Studies of these programs (e.g. Canada, Switzerland) show that returning revenue can make carbon pricing progressive – lower-income households receive more in rebates than they pay in higher fuel costs Emissions have generally declined as a result of these taxes, illustrating an environmental payoff. A key insight is that public acceptance of carbon taxes improves when revenues are transparently recycled to the public or visible projects. The U.S. can learn from Canada’s recent political backlash that even a revenue-neutral carbon tax needs strong communication – Canada’s program cut emissions and left most families better off, yet faced opposition due to visibility of the “tax” vs. less awareness of the rebate. This suggests any U.S. carbon dividend should be highly transparent (e.g. checks or clear credits labeled as carbon dividends) to win support. In cost-benefit terms, the global social benefit of carbon reductions (avoided climate damages) likely far exceeds the economic “cost” of the tax, especially when revenue is recycled. Thus, beyond fiscal impacts, this policy yields a positive net societal benefit as climate insurance.

• Financial Transaction Taxes: Many G20 countries have some form of FTT or stamp duty. We saw the UK’s stamp duty raising substantial revenue without crippling London’s role as a financial center. In France, the FTT of 0.3% on large-cap stock trades raises a few billion euros yearly and coexists with a thriving Paris stock market (though high-frequency trading there did decline somewhat). The EU’s proposed FTT (a coordinated 0.1% on shares/bonds and 0.01% on derivatives in participating countries) was projected to raise tens of billions of euros annually across the bloc, and though not all members agreed, 10 EU countries have been working on implementing it together. Their primary concern was avoidance – if only some countries tax trades, activity can shift. That’s why they pursued a collective approach. For the U.S., being home to the world’s deepest capital markets, an FTT would ideally be implemented in concert with other major markets (UK, EU, etc.), but even alone it can succeed due to the U.S. market’s size (much as a small Swiss FTT or Taiwanese FTT function in those markets). One case of caution is Sweden in the 1980s: it had a narrowly applied FTT on stock trades that led to trading volume fleeing to London, ultimately causing Sweden to repeal the tax The lesson is to make the tax broad-based and global in reach (taxing based on residence of buyer/seller and on all trading venues) to avoid such leakage. Modern proposals heed this lesson. Bottom line: Other countries’ experiences suggest an FTT is workable and can raise meaningful revenue for social needs, but design and international coordination matter to maximize benefit and minimize unintended consequences.

• Corporate Tax and Havens: The international consensus is shifting against profit shifting. The OECD Inclusive Framework (over 130 countries) agreed to institute a 15% global minimum corporate tax, reflecting a recognition that a “race to the bottom” in tax rates was harming everyone’s revenue. Already, the EU, UK, Canada, Japan, and others are implementing this minimum in 2024–2025. If the U.S. also raises its tax on foreign earnings to at least 15% (and preferably closer to the domestic 21% rate as proposedi, it will both conform to global standards and capture revenue that might otherwise go to other countries (through “top-up taxes” on U.S. firms’ profits in havens). International case studies here include the Global Forum on Transparency: over 100 jurisdictions now automatically share bank account info, as noted earlier, which has vastly reduced individual evasion options. One striking data point: by 2019, an estimated $10–$11 trillion in assets had been disclosed or located offshore under these new standards, meaning governments now have line of sight on wealth that was previously hidden. European countries also demonstrate that stronger enforcement yields results – for instance, the UK’s tax authority has a dedicated High Net Worth Unit that has significantly closed the compliance gap for the richest taxpayers, and countries like Australia and Germany have invested in data analytics to detect tax fraud (with Germany buying data leaks from tax havens leading to prosecutions). These examples support the idea that technology and cooperation can markedly improve compliance – reinforcing the proposal’s enforcement component.

• Unrealized Gains and Wealth Taxes: The U.S. would be doing something relatively novel with a direct tax on unrealized gains, but elements exist abroad. Norway and Switzerland levy annual wealth taxes (around 0.5–1% on net assets) which effectively tax the stock of unrealized gains gradually. Several European countries tax inheritances or estates at rates that capture a share of accrued gains at death (though most don’t have a pure capital gains-at-death tax). One somewhat comparable system was real property taxes – in the U.S. and elsewhere, property tax each year is akin to taxing unrealized gain on property as it appreciates. People manage to pay those (often by saving or borrowing), suggesting that with proper phase-ins, taxing wealthy people’s stock gains is feasible. Canada’s system again offers a reference: in Canada, when someone dies, their assets are deemed sold and capital gains tax is due on the estate’s final return (with some exceptions for spouses and farms). This shows taxing gains at death can be administered; Canada’s high compliance rate and functioning capital markets indicate it hasn’t deterred investment unduly. The U.S. tried a carryover basis approach in 1976, but it was repealed due to complexity concerns and lobbying – however, today’s technology and accounting practices are far more advanced, making it easier to track basis and compute gains. The key takeaway from other regimes is that the very wealthy can and do pay taxes on their assets without the sky falling; it’s more a question of political will and fine-tuning the rules to handle illiquid assets. We can look to these international practices for guidance on valuation techniques and exemptions (e.g. many countries exempt primary residences or have deferral provisions for small businesses until sale, to avoid liquidity problems – such nuances could be adopted here).

In aggregate, international comparisons confirm that broadening the tax base through these kinds of measures is not radical – many peer nations already tax carbon, financial trades, carried interest (often just as ordinary income), global corporate profits, and large fortunes in ways the U.S. does not. The U.S. has room to expand its base while still keeping rates competitive and following best practices demonstrated elsewhere.

Fiscal Impact vs. Status Quo and Alternatives

Relative to the status quo baseline, this package of tax base broadening would markedly improve the U.S. fiscal outlook over the next decade and beyond. Under current law, the CBO projects deficits from 2025–2034 to total $21.1 trillion, with annual deficits rising toward 7% of GDP – a trajectory that pushes debt and interest costs to unprecedented highs. Simply put, maintaining the status quo means continued heavy borrowing, which comes at increasing cost: net interest on the national debt is on pace to reach about $1.8 trillion per year by 2035 (over 4% of GDP), crowding out other priorities. The proposed tax measures would generate substantial new revenues to offset these deficits:

• Net Revenue Gain: Summing rough mid-range estimates, the package could raise on the order of $3–4 trillion over 10 years. This includes, for example, ~$800B from the carbon tax (if not rebated, or used to fund other tax cuts), $750B from the FTT, perhaps $1T from offshore corporate reforms, $300–500B from taxing unrealized gains, a small bump from carried interest, and say $200B net from enhanced enforcement. These are ballpark figures, but together they could average $300–400B per year in the latter half of the decade in added revenue. That would reduce annual deficits by roughly 1–1.5% of GDP, all else equal. By 2030, deficits might be a few hundred billion lower than otherwise, stabilizing debt growth to some extent. As a share of the projected $21T in baseline 10-year deficits, $3–4T in revenue is a significant dent (around 15–20% of the cumulative shortfall).

• Economic Effects: Unlike pure borrowing, raising revenue reduces the need to issue debt, thereby lowering future interest costs. For instance, avoiding $3T of additional debt issuance could save on the order of $600B in interest over 10 years (assuming a ~2% average interest rate on that avoided debt) – this secondary benefit isn’t always scored, but it accumulates beyond the initial 15-year window especially. Moreover, many of these taxes (carbon, FTT, closing evasion) have co-benefits or target economic “bads” (pollution, destabilizing speculation, tax cheating), meaning the distortionary cost to economic growth is lower than, say, raising marginal income tax rates. Some modeling (e.g. by Treasury or academic economists) indicates that smart base-broadening can raise revenue with minimal drag on GDP growth – especially if the carbon dividend boosts consumer income, or if deficit reduction leads to lower interest rates than otherwise. By contrast, the baseline path of high borrowing could itself dampen growth (through “crowding out” private investment or higher interest rates). Thus, the policy suite might improve the long-run growth outlook by fostering a more sustainable fiscal stance while also internalizing externalities (carbon) and improving financial stability (less flash trading).

• Distributional Considerations: Compared to alternatives like major spending cuts, these tax measures are generally more progressive. A carbon tax alone is regressive before rebates, but the dividend flips it to be progressive or neutral (since equal rebates benefit lower-income households most as a share of income) The FTT largely affects wealthy investors and the finance industry; closing the carried interest and estate loopholes squarely targets the rich; the global minimum tax targets profitable multinationals; and stepped-up basis reform/billionaire tax hits only the very wealthy. In contrast, broad spending cuts often hit social programs or investment that benefit wide swaths of Americans. So in a comparison: who bears the burden? This package places it primarily on high-income individuals, large corporations, and activities with negative externalities – arguably a more equitable distribution than an across-the-board spending cut or a general tax hike on wages.

• Non-Tax Alternatives: If lawmakers opted not to broaden the tax base and instead address fiscal gaps via spending cuts or more debt, there are trade-offs:

• Borrowing more: In the short run, borrowing may seem painless, but as noted, interest payments are skyrocketing – nearly $952 billion in 2025 and growing. By the early 2030s, if no fiscal changes are made, the U.S. could be spending as much on interest as it does on defense or Medicaid, limiting capacity to respond to crises. Relying on borrowing also leaves the government vulnerable if interest rates rise further. Each additional trillion in debt adds tens of billions in annual interest costs (money that buys no new services). Therefore, continuing to borrow to finance current obligations effectively transfers the burden to future taxpayers with a hefty premium.

• Cutting spending: To achieve deficit reduction comparable to, say, $300B per year by 2030, one might have to implement drastic cuts. For perspective, $300B is roughly one-third of the entire discretionary budget(which funds education, R&D, infrastructure, defense, etc.). Eliminating that solely through cuts could mean, for example, cutting defense by 50% or non-defense discretionary by 100% – politically and practically implausible without harming services and economic investments. Even trimming popular entitlement programs (Social Security, Medicare) would face major hurdles and could reduce income security for millions of seniors. Non-tax alternatives also have macroeconomic implications: cutting government spending during an economic expansion might be manageable, but during a downturn it could exacerbate a recession. By contrast, the tax measures here, especially those like carbon taxes or closing loopholes, can be phased in gradually and automatically adjust with the economy (e.g. revenue falls less in a downturn when there’s a broader base).

• Status Quo Baseline: Keeping the status quo on these tax policies means the U.S. continues to lose revenue through known inefficiencies – e.g., allowing $50–60 billion a year of capital gains to go untaxed at death, letting tens of billions in corporate profits escape to Bermuda and Cayman, and forgoing the chance to price carbon emissions (thus also forgoing the climate benefits and technological innovation a carbon price spurs). The baseline also means tolerating a large tax gap – essentially a subsidy to evaders – which is unfair to compliant taxpayers. In contrast, the proposed reforms would signal that everyone must pay their fair share, thereby potentially improving voluntary compliance (people are more willing to pay when they see others are paying too).

• Policy Synergy: Another consideration is that this suite of policies can work in tandem. For instance, revenue from a financial transaction tax or carbon tax could be used (in part) to fund transition assistance – such as clean energy investments or assistance to workers and industries affected by decarbonization. Likewise, closing the tax gap brings in revenue that can reduce the need for the more controversial measures or at least phase them in slowly. If, say, enforcement yields more than expected, lawmakers could ease the impact of a carbon tax on consumers or delay some rate increases. This flexibility does not exist with pure borrowing (debt has to be repaid regardless).

In summary, compared to the baseline of rising deficits, high debt, and minimal changes, this broadening-the-base agenda offers a fiscally responsible path that raises significant revenue, improves tax system efficiency and fairness, and produces co-benefits (climate mitigation, financial stability, reduced inequality). The costs – whether administrative investments or potential economic side effects – appear manageable and are far outweighed by the benefits in revenue and public good.

Conclusion

Over a 5–15 year horizon, implementing a carbon dividend, financial transaction tax, closing major tax loopholes, and enhancing IRS enforcement could together yield multi-trillion-dollar deficit reduction while modernizing the tax code for fairness and efficiency. The net revenue gains are substantial: roughly $300+ billion per year within a decade when fully phased in, according to various independent estimates. These funds could be used to lower federal debt growth or finance critical investments, reducing reliance on borrowing. Administrative costs – such as IRS upgrades (~$80B) or new systems for carbon dividends – are relatively small in context and themselves have high returns (e.g. enforcement paying for itself several times over). Enforcement efficiency would be dramatically improved, as demonstrated by international tax transparency efforts that have made hiding income increasingly difficult.

From a cost-benefit standpoint, the proposed tax base broadening offers a compelling value proposition. It taps into activities that either have negative externalities (pollution, speculative trading) or where the equity case for taxation is strong (large inheritances, billionaire wealth accrual, multinational profits), thus improving the overall efficiency of the tax system. It also brings U.S. policy more in line with other advanced nations’ practices, leveraging lessons learned abroad to minimize downsides. While no revenue measure is without economic impact, these largely avoid burdening working- and middle-class Americans – in fact, the carbon dividend and the curbing of tax evasion would directly or indirectly benefit typical households (through dividend checks and a fairer tax burden distribution).

Compared to the status quo baseline – persistent deficits addressed by more debt – this approach is far more sustainable. And compared to non-tax alternatives like sweeping spending cuts, it is more equitable and likely more politically palatable, since it asks those who can most afford it (wealthy individuals, large corporations) and those whose activities impose costs on society (polluters, high-frequency traders) to contribute more. In a time when interest costs are consuming a growing share of the budget, broadening the tax base is a prudent strategy to raise needed revenue with minimal sacrifice of economic growth or essential services. Indeed, by reducing deficits, it can alleviate pressure on interest rates and inflation, yielding macroeconomic benefits.

For policymakers, the key will be in the design and implementation: calibrating the carbon tax rate and rebates, setting the FTT low enough to preserve market liquidity, coordinating internationally on corporate tax rules, and giving the IRS the support to enforce laws justly. If done well, the U.S. could see, over the next 5–15 years, a significant fiscal turnaround – a lower debt-to-GDP path than baseline, more resources for public investments, and a tax system that better reflects our economic realities and values. The cost-benefit calculus strongly favors this suite of reforms: the costs are manageable and largely one-time, while the benefits (both fiscal and societal) compound over time, helping ensure long-term economic prosperity and stability.

Sources: The analysis draws on estimates from the Congressional Budget Office, Joint Committee on Taxation, and Treasury (for revenue projections), as well as case studies from OECD and various countries illustrating the impacts of similar tax measures. These sources provide a quantitative foundation for the revenue and cost figures cited throughout. The comparisons to baseline fiscal projections reference CBO’s Budget Outlook and related analyses. Each component of the proposal is grounded in real-world data, underlining the credibility of the projected net gains.