Bracket filling strategy: which bracket should you fill?
By Mario Bailey · Published · Last reviewed
The strategy is one decision repeated annually: pick a target marginal bracket, convert exactly enough traditional IRA balance to reach its ceiling, stop, and repeat until Required Minimum Distributions begin. Which bracket to target is the whole question, and it is answerable only by computing lifetime outcomes, not by comparing this year's rates. The pillar guide covers the mechanics; this page compares the targets.
Four scenarios, computed
The calculator's default scenario: married couple born 1966 and 1968, $1.4M traditional IRA, $200K Roth, $250K wages until retirement at 65, California, 6% return, 2.5% inflation, projected to age 92. Same inputs, four strategies:
| Strategy | Lifetime tax | Lifetime IRMAA | Final Roth balance | Savings vs do nothing |
|---|---|---|---|---|
| Do nothing | $952,090 | $112,435 | $1,368,118 | $0 |
| Fill the 12% bracket (recommended) | $722,878 | $112,435 | $5,388,002 | $229,212 |
| Fill the 22% bracket | $733,563 | $112,435 | $9,798,709 | $218,527 |
| Fill the 24% bracket | $785,208 | $131,510 | $10,944,944 | $147,807 |
Savings is the reduction in combined lifetime tax plus IRMAA premiums versus converting nothing. Recomputed automatically when 2026 data is refreshed.
Why the comparison is lifetime, not this-year
Paying 22% now to avoid 22% later looks like a wash. It is not, because the do-nothing path concentrates income late in life, where four mechanisms push the effective rate above the nominal bracket:
- RMDs stack automatically. At 75 the Uniform Lifetime divisor forces out $4,065 per year per $100,000 of remaining traditional balance, needed or not, and the percentage rises every year as the divisor falls.
- The survivor files single. The 22% bracket ends at $105,700 for a single filer versus $211,400 MFJ, so the same RMD income lands a widowed spouse roughly one bracket higher.
- IRMAA starts at 65. RMD-era MAGI that crosses a tier adds Medicare surcharges on top of income tax; the table's IRMAA column is exactly the premium cost each strategy buys or avoids.
- Social Security phases in. Provisional income pulls up to 85% of benefits into taxable income precisely when RMDs peak, so a marginal RMD dollar can drag $1.85 into taxable income.
The scenario table prices all four simultaneously. That is what the savings column is: not a rate arbitrage, but the cost of late-life income concentration.
The order of operations
- Project the do-nothing path and read its RMD-era marginal rate (the calculator's baseline does this).
- Pick the highest bracket ceiling whose rate sits strictly below that.
- Subtract this year's known income from the ceiling; the remainder is this year's conversion. The example page works the arithmetic on real engine output.
- Check the overlays before executing: the IRMAA lookback binds from age 63 (levers guide), the ACA 400% line binds before 65.
- Execute in December, when the year's income is measured rather than forecast; the timing guide prices the calendar boundary.
How to pick your target bracket
Target the highest bracket whose rate sits below your projected RMD-era marginal rate. For the scenario above, the engine recommends the 12% ceiling; the table shows exactly what the larger conversion paths would do to lifetime tax, IRMAA premiums, and the final Roth balance. A larger traditional balance, a higher expected return, or a move to a no-tax state can shift the answer up a bracket. The target is computed, not guessed: run your own inputs rather than borrowing this table.
Two constraints bound the strategy every year: conversions must complete by December 31 (not the April filing deadline), and in any year an RMD is due, the RMD must be withdrawn before any amount is converted. All the rules.