Retirement & Income

By the Retiree Report Editorial Team · Updated 2026-05-07 · 7 min read

This article is general information, not financial, tax, or legal advice. Consult a licensed professional before acting on it.

The Roth conversion window before Social Security

If you’ve stopped working but haven’t yet filed for Social Security, you’re sitting in what financial planners call a tax valley. Wages have ended, required withdrawals haven’t started, and benefits aren’t flowing yet. For many people that gap is the lowest-income stretch they’ll see in retirement — and a chance to move money out of a traditional IRA into a Roth before the bill grows.

A Roth conversion shifts pre-tax retirement dollars into a Roth IRA. You pay ordinary income tax on the converted amount in the year you do it. After that the money grows tax-free, and qualified withdrawals never count toward your taxable income. There are no income limits on conversions and no annual cap on the amount.

Why these years can be your lowest-tax stretch

Picture a typical retirement year before benefits begin. Earned income is gone. Social Security hasn’t started, so your provisional income is small. Required minimum distributions from a traditional IRA or 401(k) don’t kick in until age 73 for anyone born between 1951 and 1959, and age 75 for those born in 1960 or later under the SECURE 2.0 changes the IRS describes in its retirement plan and IRA FAQs.

That means a 65-year-old who retired at 64 and plans to delay Social Security to 70 may have five years where taxable income is mostly interest, dividends, and a few thousand dollars from a brokerage account. The 2026 standard deduction is $32,200 for a married couple filing jointly and $16,100 for a single filer, per the IRS inflation adjustments announced in late 2025. The 12% bracket runs up to $100,800 of taxable income for joint filers and $50,400 for single filers.

Translate that into real numbers. A retired couple with $40,000 of investment income and no other earnings can convert roughly $93,000 from a traditional IRA to a Roth and still pay no more than 12% on the conversion itself. Once benefits begin and RMDs kick in, the same dollar of conversion may land in the 22% bracket — or push Social Security into taxation that wasn’t there before. The window closes on its own.

How a Roth conversion actually works

The mechanics are simpler than the planning around them. You instruct your IRA custodian to move part of a traditional IRA balance into a Roth IRA in your name. The dollar amount you move counts as ordinary income that year, on top of whatever else you earn. You report the conversion on Form 8606 with your 1040, as the IRS lays out in Publication 590-A. Vanguard, Fidelity, and Schwab all process conversions online in a few clicks, but the tax effect is yours alone to manage.

Two technical details matter. First, the pro-rata rule: if you have any pre-tax money in a traditional, SEP, or SIMPLE IRA anywhere, the IRS treats every conversion as a proportional mix of pre-tax and after-tax dollars across all of those accounts combined. You can’t cherry-pick the after-tax slice. Second, since 2018, conversions are permanent. The old “do-over” — recharacterizing a conversion when the market dropped — is gone. Whatever amount you move and report, you owe tax on for that year.

Pay the conversion tax from money outside the IRA, ideally a taxable brokerage or savings account. Withholding the tax from the converted amount shrinks the Roth balance and, if you’re under 59½, can trigger an early-withdrawal penalty on the part withheld. People who skip this detail end up with a smaller Roth than the spreadsheet promised.

Two ceilings to watch: tax brackets and IRMAA

The most common Roth conversion mistake isn’t doing it — it’s converting a dollar too many. Bracket creep is the obvious one. Push past the top of the 12% range and the next dollar costs 22 cents in federal tax instead of 12. Specialty bracket effects can be even sharper: long-term capital gains taxed at 0% can suddenly become taxable at 15% once your ordinary income crosses certain thresholds, and Social Security itself has a fixed-threshold tax structure that hasn’t changed since the 1980s.

The Social Security part surprises people. The IRS uses provisional income — adjusted gross income plus tax-exempt interest plus half of your benefits — to decide how much of your Social Security check is taxable. For joint filers, up to 50% of benefits become taxable above $32,000 of provisional income, and up to 85% above $44,000, as the IRS explains in its Social Security income FAQ. For single filers the thresholds are $25,000 and $34,000. Those numbers were set in 1983 and 1993 and aren’t indexed for inflation, so an ordinary middle-class retiree with even modest other income usually crosses them. A Roth conversion done in a year you’re collecting Social Security will almost certainly bump more of those benefits into taxable territory — which is why the years before you claim are so attractive for conversions.

The second ceiling is IRMAA, the income-related surcharge on Medicare Part B and Part D. Once you’re 65 and on Medicare, your premium can jump if your modified adjusted gross income crosses certain thresholds. For 2026, IRMAA begins at $109,000 for single filers and $218,000 for joint filers, and the standard Part B premium is $202.90 a month, according to the Centers for Medicare & Medicaid Services. AARP reports that 2026 is the first year the standard premium has crossed $200.

The trap is the lookback. IRMAA uses your tax return from two years prior, so a Roth conversion in 2026 is what determines whether you pay an IRMAA surcharge in 2028. A couple that converts $250,000 in 2026 will see a higher Medicare bill in 2028 even if their 2027 income is back to normal. We’ve broken down the full IRMAA tier table in our guide to the 2026 IRMAA income thresholds, and the same lookback logic applies for any year you convert.

How to size and time the move

There isn’t a single right answer, but there’s a usable framework. Run a rough projection of your taxable income for each year between now and the year RMDs begin. Then ask: what’s the gap between that projected income and the top of the bracket I’m willing to pay into? That gap, minus a buffer for surprises like a capital gain or an inherited IRA, is the conversion ceiling for that year.

Most people who do this seriously spread conversions over multiple years rather than doing one large move. A five-year conversion ladder lets you stay under bracket and IRMAA limits each year, even if it leaves some traditional balance behind to handle with RMDs. The closer you get to age 73 — or 75, depending on your birth year — the harder it gets to convert without colliding with required distributions, which we cover in our explainer on RMD rules under SECURE 2.0.

A few other considerations don’t get enough attention. State income tax matters: a conversion done before a move from a high-tax state to a no-tax state may cost more than the same conversion done after. Estate planning math also shifts the calculus — a Roth left to heirs comes with a 10-year withdrawal clock, but those withdrawals are tax-free. And if a spouse is likely to file as a single survivor for several years, conversions that smooth the surviving spouse’s bracket can be worth more than the surface arithmetic suggests, because single brackets are narrower than joint ones at every level.

The IRS publishes a free Tax Withholding Estimator that can help you project the bill before you pull the trigger, and your IRA custodian’s online conversion form usually shows a preview of the year-end 1099-R. None of this should replace a conversation with a CPA or a fee-only financial planner who can model the multi-year picture. The math is unforgiving when it goes wrong, and the rules around the pro-rata calculation and Form 8606 trip up even careful filers.

What to remember

The years between retirement and your first Social Security check are short, finite, and usually the lowest-tax stretch you’ll have left. A Roth conversion done well in that window can move tens of thousands of dollars out of a future RMD bill, off the Social Security taxation table, and into a balance your heirs will eventually inherit tax-free. A conversion done poorly will tip you into a higher bracket, an IRMAA surcharge two years later, or both. The work is in modeling the gap year by year, sizing each conversion to a specific ceiling, and accepting that this is a one-way move once the December 31 deadline passes. None of this is tax advice; it’s a sketch of the terrain. Talk to a CPA or fee-only planner before making a conversion that affects your tax return.