Roth Conversion Bracket Filling: How Much to Convert Each Year

Why One-and-Done Conversions Are Costly

The U.S. tax system is progressive: the more income you have, the higher the rate on the next dollar earned. Converting a large traditional IRA balance all at once creates a single enormous income spike, pushing hundreds of thousands of dollars through the highest brackets. A $500,000 conversion in a single year might face 22%, 24%, 32%, and 35% rates on different portions — with perhaps $150,000 or more owed in federal tax alone.

Spreading that same $500,000 across ten years at $50,000 per year — each year carefully calibrated to stay within the 22% bracket — could cost roughly $60,000 total in federal tax instead. The multi-year approach isn't just slightly better; it can cut the total tax bill by 50–60% over a single large conversion.

The Bracket-Filling Approach Explained

The bracket-filling approach works like this: each year, you project your total taxable income (pension, Social Security, dividends, capital gains, interest) and compare it to the top of your target tax bracket. The gap between your current income and that ceiling is your conversion budget for the year.

The Roth Conversion Ladder

A Roth conversion ladder is a variation of the multi-year approach designed for retirees who need access to Roth funds before age 59½. Because each conversion starts a new five-year clock before the converted principal can be accessed penalty-free, a ladder stages conversions to create a stream of maturing, accessible funds year by year.

For example, if you convert $40,000 in Year 1, another $40,000 in Year 2, and so on, the Year 1 conversion becomes fully accessible (penalty-free) in Year 6. By Year 10, you have a steady stream of tax-free principal becoming available each year. This strategy is particularly useful for early retirees who need income between retirement and age 59½ without triggering penalties.

Projecting Future Tax Rates to Determine How Much to Convert

The case for multi-year conversions rests on the assumption that your future marginal rate will be higher than your current rate. To test this, project your income at ages 70, 73, 75, and 80 — accounting for:

• Social Security benefit amount at your planned claiming age
• RMDs from current traditional IRA and 401(k) balances, projected with reasonable growth
• Any pension income
• Expected investment income from taxable accounts

If this projection shows your income rising substantially — as it does for most retirees with significant traditional IRA balances — the case for converting now at lower rates is strong. A financial planning tool or advisor can model this precisely.

The TCJA Sunset: A Time-Limited Opportunity

The Tax Cuts and Jobs Act of 2017 reduced ordinary income tax rates significantly — the 22% bracket was previously 25%, and the 24% bracket was previously 28%. These reduced rates are currently scheduled to expire after 2025, reverting to pre-TCJA levels unless Congress acts.

If rates increase as scheduled, the cost of Roth conversion rises immediately. Retirees who execute conversions during the low-rate window have the opportunity to lock in current rates permanently on the converted balance. This makes the years 2025 and potentially 2026 particularly attractive for accelerated conversions in affected brackets.

Adjusting the Strategy Annually

A multi-year strategy is not a "set it and forget it" plan. Every year brings changes: new tax laws, changing account balances, unexpected income events, health changes, or shifts in Social Security claiming plans. The conversion amount should be recalculated each year based on current-year income projections and updated to reflect any changes in the tax landscape.

Rebalancing inside the Roth IRA itself is also relevant. As the Roth balance grows, the asset allocation should be reviewed to ensure the tax-free bucket is invested for long-term growth — there's no benefit to holding cash or bonds in an account that grows tax-free.

When to Stop Converting

Roth conversions become less attractive when:

• Your marginal conversion rate approaches or exceeds your expected retirement rate
• The conversion would trigger IRMAA surcharges that exceed the tax savings
• The traditional IRA balance has been reduced to the point where future RMDs will be modest
• You need the taxable funds used to pay conversion taxes for other expenses
• Your health outlook has changed and the break-even horizon has shortened

There is no single rule for when to stop — it requires an annual reassessment of the trade-off between current conversion cost and projected future tax savings.