There is a stretch of years in many retirements when taxable income falls off a cliff. You stopped working. You have not claimed Social Security yet. Required minimum distributions are years away. Your tax bracket has never been lower and may never be this low again. That window is the best deal on Roth conversions you will ever get, and most people let it close unused.
Should you do Roth conversions before claiming Social Security? In most cases, yes, and the reason is arithmetic, not philosophy. Converting during those gap years lets you pay tax at 10 or 12 percent. Wait until Social Security and RMDs are both running, and the same dollars get taxed at 22 percent or more. The difference over a decade of conversions can be tens of thousands of dollars.
Why the gap years are the cheapest conversions of your life
Picture a couple who retires at 62 and delays Social Security to 70. For eight years their income is just what they pull from savings. Say they have $60,000 of headroom in the 12 percent bracket each year. They convert $60,000 a year, paying $7,200 in tax per conversion year. Over eight years they move $480,000 into Roth at a 12 percent rate.
Now picture the alternative: no conversions, and at 73 the RMDs start on a traditional IRA that has kept growing. Stack a large RMD on top of two Social Security checks and the couple that was in the 12 percent bracket at 64 is in the 22 percent bracket at 76, paying nearly double the rate on the same dollars. It gets worse for the survivor. When one spouse dies, the other files single, where the brackets are roughly half as wide. The RMD does not shrink but the tax rate jumps. Converting while both spouses are alive, in the low-income window, defuses that.
The stacking problem you avoid by going early
The timing matters because of how Social Security taxation works. Social Security taxation runs on provisional income: your adjusted gross income plus half your benefits plus some nontaxable interest. Cross $25,000 single or $32,000 married and up to 50 percent of benefits become taxable. Cross $34,000 single or $44,000 married and up to 85 percent is taxable. Those thresholds have not moved since the 1990s.
A Roth conversion raises your adjusted gross income in the year you do it. Do it after benefits start and the conversion stacks on top of your Social Security, dragging more of your benefits into the taxable tiers. You pay tax on the conversion and tax on a bigger slice of your benefits, and you may trip IRMAA surcharges on Medicare premiums too. Do the conversion before benefits start and there is nothing to stack onto. The conversion is taxed cleanly at your ordinary rate with no ripple effects. Roth withdrawals later do not count in the Social Security formula at all, which is the quiet payoff: a big Roth balance means decades of income that never touches provisional income.
The honest counterargument: delaying Social Security to 70 means funding eight years of life from savings, which is not comfortable for everyone. If you need the check at 62 to eat, take the check. But if you can bridge the gap with taxable savings, the combination of delayed benefits (about 8 percent more per year waited) and cheap conversions in the window is the strongest play in retirement tax planning. One guardrail while you execute: watch the IRMAA thresholds as you approach 65, since conversion income counts toward the Medicare premium lookback.
Frequently asked questions
Is it better to do Roth conversions before claiming Social Security?
Usually yes. Between retirement and your claim, taxable income is often at its lifetime low. Converting then lets you pay 10 or 12 percent instead of 22 percent or more later, when RMDs and Social Security stack.
Do Roth conversions make your Social Security taxable?
Conversions done after benefits start can, because the conversion income raises adjusted gross income and pushes more benefits into the taxable tiers. Conversions before benefits start avoid this, and Roth withdrawals later do not count in the formula.
How many years should you do Roth conversions before Social Security?
As many gap years as you have. Retire at 62 and delay to 70 and you may have 8 years of room. RMDs start at 73 or 75 depending on birth year, which sets the far end of the window.
Can Roth conversions increase Medicare premiums?
Yes. Conversion income counts toward the MAGI that sets IRMAA surcharges on Part B and D. Plan amounts to stay under the thresholds in the years before the age-65 lookback.
What is the biggest mistake with Roth conversion timing?
Waiting too long and losing the low-income window. Once Social Security and RMDs both start, your bracket is set and conversions get expensive.
Model your conversion ladder year by year
Sources: IRS provisional income thresholds for Social Security taxation; RMD age rules under SECURE 2.0; IRMAA MAGI thresholds. Verified October 2026. This is general information, not tax advice.