Between the day you retire and the day Social Security and required minimum distributions begin, many retirees pass through “gap years”, low income years when their tax bracket temporarily collapses. A Roth conversion in a gap year moves money from a pre tax account to a Roth at today’s low rate, shrinking the future RMDs that would have been taxed higher. This guide explains the strategy, the math, and the pitfalls. Educational content, not financial advice.
What gap years are
Picture retiring at 62. Social Security might not start until 67 or 70, and RMDs begin years later at the age current law sets. Between 62 and those milestones, your taxable income may consist of little more than dividends and a small pension, perhaps the lowest earning years of your adult life. Those are gap years: a window when you can recognise extra income (via Roth conversions) at unusually low tax rates before the government starts forcing income out of your accounts on its schedule.
How a Roth conversion works
A conversion moves dollars from a traditional IRA or 401(k) into a Roth account. You pay ordinary income tax on the converted amount now; afterwards, the money grows tax free and qualified withdrawals are tax free. There is no age limit and no income limit on conversions themselves. The strategic question is never whether you can convert, it is when the tax price is cheapest. Gap years are frequently the answer.
The bracket filling strategy
The classic move is “filling the bracket”: convert just enough each year to use up your current low tax bracket without spilling into the next one. Consider a hypothetical couple with $30,000 of pension income and, hypothetically, $60,000 of remaining room in their current bracket. (Bracket thresholds adjust yearly, verify the current tax year’s figures with the IRS.) They convert $60,000, paying roughly $7,200 in tax at a hypothetical 12% rate, ideally from a taxable account rather than from the converted funds so the full $60,000 keeps compounding in the Roth.
Repeat for several gap years and the effect compounds twice: less pre tax money means smaller future RMDs, and the converted money grows free of future tax. A Roth conversion calculator in our free tools hub can help you model how much room your own bracket has.
What can go wrong
Conversions are irreversible, since 2018 you cannot “recharacterise” and undo one, so a conversion that looked clever in January is permanent by December. Overshooting your bracket wastes the strategy’s whole point. Converting can raise Medicare premiums two years later through income based surcharges, and before 65 it can shrink marketplace health insurance subsidies. The pro rata rule means if you hold both pre tax and after tax dollars in traditional IRAs, each conversion is partly taxable regardless of which dollars you “meant” to convert. And paying the tax from the converted amount itself both shrinks the Roth and can trigger penalties if you are under the early withdrawal age.
Coordinating with RMDs and Social Security
Think of gap year conversions as a race against two clocks. Every dollar converted is a dollar that will not be forced out later as an RMD, so conversions directly defuse the RMD April 1 trap and the bracket creep of your seventies. Meanwhile, delaying Social Security to 70 while living off conversions and taxable savings is a common pairing: you buy larger inflation adjusted benefits later while paying conversion tax at low rates now. Map the whole timeline, conversions, Social Security start, RMD start, before converting a single dollar.
Sketching a multi year conversion plan
Suppose a hypothetical retiree has eight gap years, ages 62 to 70, and $400,000 in a traditional IRA. Converting $50,000 a year fills the low bracket annually, moves the full $400,000 to Roth by 70, and, because the pre tax balance shrinks each year, steadily reduces the RMDs that would otherwise begin later. The plan needs annual maintenance: re check income each December, adjust for market moves (a down year is a cheaper conversion year), and pause if income spikes unexpectedly. Treat it as a multi year project with yearly reviews, not a one time decision.
A worked example: converting $200,000 across four gap years
Here is the strategy with real numbers attached. Every rate in this example is an explicitly stated assumption for illustration, tax brackets, thresholds and Medicare premium tiers change, so verify the current tax year’s figures before acting on your own version of this plan. Assume a married couple retire at 63 with $600,000 in a traditional IRA, $40,000 a year of other taxable income, no wages, and four clear gap years before other income sources begin. To keep the arithmetic transparent, the example ignores investment growth; in real life the balances would move each year and the plan would be re checked annually.
Step 1, choose an annual conversion amount. The couple decide to convert $50,000 a year for four years. Total converted: 4 × $50,000 = $200,000. Their pre tax IRA balance falls on paper from $600,000 to $600,000 − $200,000 = $400,000, again ignoring growth.
Step 2, price each conversion. Assume the converted dollars are taxed at a flat 12% for this illustration. Each year’s tax bill is $50,000 × 12% = $6,000, and the four year total is 4 × $6,000 = $24,000. They pay that tax from a taxable savings account, so the full $50,000 lands in the Roth each year and starts growing tax free immediately. You can sanity check your own income picture with our US income tax calculator before sketching a conversion amount, the bracket you are filling is the whole strategy, so it deserves real figures rather than guesses.
Step 3, compare the alternative ending. Suppose, purely as an assumption, that the same $200,000 had stayed pre tax and was eventually withdrawn at a 22% rate instead. The tax would be $200,000 × 22% = $44,000. Against the gap year cost of $24,000, that is a difference of $44,000 − $24,000 = $20,000 in this simplified illustration. That gap is the entire prize the strategy is chasing, and it exists only because of the assumed rate difference. If your real future rate turns out to be the same as your gap year rate, the headline saving shrinks to roughly zero and only the secondary benefits remain.
Step 4, see what happens to future forced income. Required minimum distributions are calculated as a percentage of the pre tax balance, so a smaller balance means a smaller forced withdrawal at any given percentage. Using a purely illustrative 4% to show the shape of the effect: 4% of $600,000 is $24,000 a year of forced income, while 4% of the post conversion $400,000 is $16,000 $8,000 a year less income being pushed into whatever bracket the couple occupies in their seventies. Actual RMD percentages come from IRS tables and rise with age; the point here is the direction and rough scale, not the 4% figure itself. Project the long term picture with our retirement calculator alongside any conversion plan.
Spreading conversions out vs converting in one big year
The worked example spreads $200,000 over four years. The obvious shortcut, converting it all at once, usually destroys the point of the exercise, because one huge conversion stacks on top of that year’s other income and pushes deep into higher brackets. This table compares the two shapes using the same stated assumptions as the example, plus a hypothetical 24% assumed rate for the single year lump:
| Spread over four gap years | All in one year | |
|---|---|---|
| Timing | Four annual conversions, ages 63 to 66 | One conversion in a single year |
| Amount per conversion | $50,000 | $200,000 |
| Assumed tax rate (illustration only) | 12% each year | 24% on the lump |
| Total tax in this illustration | $24,000 | $48,000 |
| Pre tax balance left (ignoring growth) | $400,000 | $400,000 |
| Main risk | Needs four years of discipline and an annual income review | One very large tax bill and one very high income year, which can also raise Medicare premiums two years later |
Note what does not differ between the columns: the amount converted and the balance left behind are identical. The whole $24,000 difference in the table comes from the price paid per dollar converted. That is why experienced converters obsess over annual income estimates and December check ins rather than over the conversion paperwork itself, which takes minutes.
Common mistakes in gap year conversions
The strategy is forgiving of small errors but not of these six:
- Converting first and estimating income later. A conversion done in February is priced by the income you eventually report the following April, including the capital gain, bonus or business income that arrived in October. Because conversions cannot be undone, an overshoot is permanent. Fix: convert in stages through the year, do the final and largest tranche in December when your income is nearly certain, and leave a margin below the top of your target bracket.
- Paying the tax out of the conversion itself. If $50,000 is converted but $6,000 is withheld for tax, only $44,000 reaches the Roth, and if you are under the early withdrawal age, the withheld portion can also attract a penalty. Fix: hold the tax money in an ordinary savings account before you convert, and treat “we cannot pay the tax from outside the IRA” as a reason to convert less, not as a detail to solve later.
- Forgetting the two year Medicare lookback. Medicare’s income related premium surcharges (IRMAA) are based on your tax return from two years earlier, so a conversion at 64 can raise the premiums you pay at 66, precisely when you first enrol. Many couples discover this only when the premium letter arrives. Fix: before setting a conversion amount at ages 63 and up, check where the resulting income lands against the current IRMAA tiers; our Medicare cost and IRMAA calculator exists for exactly this check.
- Ignoring the pro rata rule. If your traditional IRAs hold any after tax, nondeductible contributions, the IRS treats every conversion as a proportional blend of pre tax and after tax money across all your traditional IRAs. You cannot point at the after tax dollars and convert only those. Fix: total up all your traditional IRA balances and their after tax basis before converting, and expect part of every conversion to be taxable even in an account you think of as “the after tax one.”
- Letting a conversion wreck a health insurance subsidy. Retirees under 65 buying marketplace coverage may receive premium subsidies based on household income, and a large conversion raises that income dollar for dollar. A conversion that saves tax at one rate can quietly cost more than that in lost subsidy. Fix: if you buy your own coverage before Medicare age, model the conversion’s effect on your subsidy first and size the conversion to the subsidy threshold, not just to the tax bracket.
- Setting the plan once and never revisiting it. Gap years are not identical: a market drop makes conversions cheaper, a one off gain makes them expensive, and a move to a different state changes the state tax side of the price. Fix: re run the numbers every autumn, income estimate, bracket room, Medicare lookback, state of residence, and be willing to convert less, or nothing, in a year when the price is wrong.
None of these mistakes requires expertise to avoid; they require a calendar. The households who get the most from gap year conversions are rarely the ones with the cleverest single conversion. They are the ones who repeat a modest, correctly priced conversion several years in a row and skip the years when life makes the price wrong.
Frequently asked questions
How do I know how much to convert each year?
Project your taxable income for the year, subtract it from the top of your target bracket (using the current tax year’s IRS thresholds), and convert the difference. Many people do this in December when income is nearly certain, or convert in chunks through the year.
Can I undo a Roth conversion if markets fall?
No. Recharacterisation of Roth conversions was eliminated starting in 2018. Convert only amounts you are comfortable paying tax on even if the market drops the next day.
Should I convert if I expect the same bracket in retirement?
It is roughly a wash on pure tax math, but secondary benefits can still favour converting: no RMDs on the Roth, tax free inheritance for heirs, and protection against future rate increases. Run the full picture, not just the bracket.
What is the pro rata rule?
If your traditional IRAs contain both pre tax and after tax (nondeductible) money, the IRS treats every conversion as a proportional mix of both. You cannot cherry pick just the after tax dollars. This surprises people attempting “backdoor” strategies with existing pre tax balances.
Do state taxes matter for conversions?
Yes. Converting while living in a no income tax state and retiring in a high tax one (or vice versa) changes the math meaningfully. Factor your current and expected future state into the decision.
Should I convert during a market downturn?
Often yes, converting depressed shares means paying tax on a lower value, then letting the recovery happen inside the tax free Roth. It is one of the few genuine silver linings of a market drop for retirees with cash available to pay the tax.