Planning for Retirement in an Era of Tax Rate Uncertainty

The Assumption Built Into Every Tax-Deferred Account

When you contribute to a traditional 401(k) or IRA, you are making a specific bet. You are betting that your tax rate in retirement will be lower than your tax rate today. If that bet is right, deferral saves you money. If it is wrong, you pay more in taxes over your lifetime than if you had never deferred at all. This is not a small bet. On a $1 million tax-deferred account, a 5 percentage point difference in your effective withdrawal rate - say, 22% versus 27% - is $50,000 over the life of the account in present-value terms. On a $2 million account distributed over 25 years, the difference compounds to well over $100,000. The tax rate assumption embedded in most retirement planning is that rates will be similar to or lower than today. That assumption is based partly on the belief that retirement income will be lower than working income, and partly on the assumption that tax law will remain roughly stable. Both assumptions deserve scrutiny. The Tax Cuts and Jobs Act of 2017 reduced marginal rates across most brackets. Under current law, those reductions are set to expire. The top rate would increase. Brackets would shift. For someone currently in the 22% bracket, the effective change might be modest. For those in the 32% or higher bracket, the exposure is more meaningful. But the TCJA sunset is only one data point. Tax rates have changed dramatically across virtually every decade of American history. The top marginal rate was 94% in 1944 - in response to World War II spending. It was 70% as recently as 1980. It dropped to 28% in 1988 before climbing again. Anyone who confidently predicts where rates will be in 2040 is guessing.

Why Long-Term Rate Increases Are Structurally Likely

Predicting specific tax legislation is impossible. But examining the underlying fiscal dynamics gives a clearer picture of the pressures shaping future rates. The federal debt exceeded $36 trillion in recent years and continues growing. Interest payments on that debt now consume a significant portion of the federal budget. Social Security and Medicare face long-term funding shortfalls that actuaries have documented for decades. The Social Security trust fund is projected to be depleted in the mid-2030s without legislative changes - at which point benefits would be reduced or taxes would need to increase. None of this is politically certain. But the direction of fiscal pressure is clear: more spending needs, constrained revenue, and a demographic shift as Baby Boomers move from taxpayers to benefit recipients. The Congressional Budget Office's long-range projections consistently show rising debt-to-GDP ratios under current policy. For a 55-year-old planning a 30-year retirement, the question is not what tax rates will be next year. It is what they will be in 2035, 2045, and 2055. The honest answer is: nobody knows. And that uncertainty itself argues for not concentrating all retirement savings in accounts where the future tax rate determines how much you keep.

Tax Diversification as the Rational Hedge

The solution to rate uncertainty is not to predict rates correctly. It is to build a portfolio that performs well under multiple rate scenarios. Tax diversification means holding balances across three types of accounts: pre-tax accounts like traditional IRAs and 401(k)s, after-tax Roth accounts, and other tax-free sources. In retirement, you draw from each bucket strategically based on your current-year tax situation. In a low-rate environment, drawing more from pre-tax accounts makes sense - you pay tax at favorable rates. In a high-rate environment, drawing from Roth accounts and other tax-free sources keeps your taxable income lower. If rates remain stable, you blend the two as needed to manage brackets. This flexibility is worth real money. A retiree with $800,000 in a traditional IRA and nothing in Roth has no flexibility - every dollar of retirement income is taxable at whatever rate happens to apply. A retiree with $500,000 in traditional and $300,000 in Roth can choose each year which bucket to draw from, optimizing for the current rate environment. The Roth 401(k) contribution limit in 2026 is $24,500 for those under 50 - the same as the traditional 401(k) limit, with no income restrictions. Workers ages 60 to 63 can contribute up to $35,750 with the SECURE 2.0 enhanced catch-up. Building Roth balances now, while there is still time, is the most direct hedge against the possibility of higher future rates.

The Cost of Betting Everything on One Outcome

A concentrated tax-deferred strategy - putting everything into traditional accounts and assuming rates will be lower in retirement - is a high-conviction bet. Like any high-conviction bet, the payoff can be excellent if you are right and costly if you are wrong. Consider two scenarios for a married couple retiring with $1.5 million in tax-deferred accounts. In the first scenario, rates stay roughly where they are and the couple manages income carefully, paying an average effective rate of 18% on withdrawals over 25 years. Total taxes paid: approximately $270,000. In the second scenario, rates rise modestly - 5 percentage points across their relevant brackets - and their effective rate averages 23%. Total taxes paid: approximately $345,000. The difference is $75,000 over 25 years - a meaningful sum that could have funded two or three years of retirement spending. That $75,000 gap could be substantially reduced or eliminated by building even a partial Roth balance during working years. The cost is paying some tax now - at known, current rates - rather than deferring all of it to an unknown future rate. The 2026 standard deduction for married filers is $32,200. After that deduction, the first $24,800 of taxable income is taxed at just 10%, and income up to $100,800 taxable is taxed at 12%. These low bracket rates may not persist indefinitely. Filling them with Roth conversions now - rather than building larger tax-deferred balances that will be taxed at unknown future rates - is the structural hedge against rate uncertainty.