The 12% Bracket Ends at $100,800 for a Couple This Year. A Retired Couple With No Paycheck Can Convert Right Up to That Line by Dec. 31. Most Never Look Up the Number

The Internal Revenue Service sets a 12% federal income tax bracket that, for a married couple filing jointly, runs up to $100,800 in taxable income for the current tax year. That single figure anchors a decision most retired couples never make on purpose: how much of a traditional IRA or 401(k) to convert to a Roth before December 31.

Taxable income is the key phrase, and the $100,800 ceiling sits on top of the standard deduction, which the IRS puts at $32,200 for a couple filing jointly this year. Money received and taxable income are two different measurements. The deduction comes off first, then the bracket layers start from zero. Confusing the two is the most common error people make when they try to size a conversion on their own.

Why Retirees Often Sit Far Below the Line

Between the last paycheck and the first required minimum distribution, a couple’s taxable income can be surprisingly modest. Some interest from cash or CDs, some dividends from a brokerage account, perhaps a pension, and Social Security, of which only a portion is taxable. Together, the total often lands well below the top of the bracket. The distance between where their taxable income falls and where the 12% bracket ends is unused conversion capacity, and the Internal Revenue Service says you can measure it directly. Pull last year’s return, adjust for anything that has changed, and the gap is right there.

The IRS publishes the figure every year and adjusts it for inflation, yet almost nobody looks at it. Those low-tax years between the last paycheck and the first required withdrawal are the whole subject of a free guide we put together on the Roth window. The couples who use it are the ones who bothered to check.

What Filling the Bracket Buys

The comparison worth thinking about pits a known 12% rate now against an unknown, likely higher rate later, once required minimum distributions begin and the account has continued to grow, or once one spouse dies and the survivor files as a single taxpayer, according to the Internal Revenue Service. Single filers hit each higher bracket at roughly half the income level a couple does, which means the same annual withdrawal that fit comfortably at 12% during joint filing can land in a much higher bracket the year after a spouse’s death, according to the Internal Revenue Service. This dynamic is often cited as a reason to convert while both spouses are alive and the joint brackets are available.

Every dollar converted at 12% is a dollar that will never be withdrawn later at 22% or 24%, according to the IRS. The Roth then grows without further federal income tax and carries no lifetime required distribution for the original owner.

Why December 31 Is the Real Deadline

Unused bracket room does not roll forward. A couple who converts nothing this year gets a fresh bracket next year of the same size, and this year’s opportunity simply disappears. A conversion must be completed within the calendar year to count for that year’s taxes, meaning the assets have to move from the traditional account into the Roth by December 31. Custodians get backed up in December, so the practical cutoff runs a couple of weeks earlier than the legal one. Paperwork started on the 30th often fails to settle in time.

What Quietly Eats the Room

A conversion raises income, and other pieces of the tax code respond to income in ways that shrink the room a naive calculation would suggest.

Social Security is the biggest one. As other taxable income rises, a larger portion of the couple’s benefits becomes taxable, so a conversion can increase taxable income by more than the converted amount. Long-term capital gains and qualified dividends sit in their own layered rate system that stacks on top of ordinary income, and filling the ordinary bracket can affect how those layers are taxed. If either spouse is on Medicare, higher income this year can raise Part B and Part D premiums about two years later, because those adjustments run on a lookback.

And for early retirees buying health coverage through the marketplace before Medicare eligibility, the premium subsidies phase out as income rises, which can make a conversion far more expensive than the bracket rate alone implies. These interactions are why many advisors suggest leaving a margin rather than filling the bracket to the last dollar.

How Couples Actually Run the Numbers

The mechanics are straightforward. Estimate this year’s taxable income before any conversion, using the most recent pay stubs, brokerage statements, and Social Security records. Subtract that from the top of the 12% bracket to find the room, according to the Internal Revenue Service. Convert somewhat less than that amount to leave a buffer for the interactions above. Pay the resulting tax from money outside the retirement account so the full converted amount stays invested and compounds inside the Roth. Then repeat the exercise next year, because the bracket ceiling moves with inflation and this year’s number will not be next year’s.

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