A $500,000 Roth Conversion in Retirement, Priced Year by Year

Why the first $50,000 costs almost nothing

Money in a traditional 401(k) or IRA is shared with the IRS, and the IRS gets to decide when to send the bill. A Roth conversion in retirement lets you pick when you pay it. What sets the price is whatever the conversion collides with on your tax return in the years after you stop working. Here's a $500,000 conversion priced from start to finish.

Take a couple who retire at 62 with $1.2 million in a traditional IRA and $850,000 in a taxable brokerage account. They spend about $105,000 a year, they live off the brokerage account, and they won't claim Social Security until 70.

At 65, before they convert anything, their tax return shows no wages, no Social Security and no required distributions. It shows about $56,000 of dividends and long-term capital gains from the brokerage account, and for a married couple that $56,000 carries zero federal income tax.

Their joint standard deduction at 65 is $35,500. When they convert their first $50,000, $35,500 of it disappears into that deduction. The remaining $14,500 sits in the 10% bracket, so the federal bill is $1,450. That's less than three cents on the dollar.

The second $50,000 costs nearly seven times as much

Convert a second $50,000 in the same year and it costs about $9,900. Their spending hasn't changed. The capital gains have. The 0% rate on long-term gains applies while total taxable income stays under $98,900. After the first conversion, their taxable income sat around $72,000 and the gains stayed tax-free. The second $50,000 pushes taxable income to $126,000, well past that line.

Part of the $9,900 is ordinary tax as the conversion steps into the 12% bracket. The other $4,100 is brand new tax on capital gains that used to be completely free. The conversion collided with their brokerage income and set off a second tax bill, and that collision is where the real cost sits.

What leaving the IRA alone costs

Doing nothing has a price too. At a modest 5% real growth rate after inflation, the $1.2 million grows to $2.26 million by age 75. That's when required minimum distributions start for anyone born in 1960 or later, and this couple's first one is about $92,000.

They don't get a vote. Add Social Security and they have $165,000 of mandatory income they never asked for. Money that could have been converted at 10% in their 60s now comes out at closer to 22%. The required percentage climbs every year, and by 92 the distribution alone is $170,000, pushing their annual income to $245,000. The bill keeps growing on a timetable the IRS writes.

The same $100,000 at three different ages

I priced the same $100,000 conversion at three ages for the same couple and portfolio. Only the calendar changes.

At 63, it costs about 30% all-in, or $30,000 to move $100,000. They're buying health insurance on the ACA marketplace, and their premium subsidy depends on their income. In 2026 that subsidy cuts off entirely at $84,600 for a two-person household. Their base income is $55,000, which leaves roughly $29,000 of headroom. A $100,000 conversion blows past the limit, and they lose the whole subsidy for the year: $17,000 in lost health savings on top of the federal tax.

From 65 through 69, the same conversion costs 11%. Medicare has started, so there's no subsidy to lose. Social Security hasn't been claimed, and RMDs are still a decade away. The $100,000 lands on a return with nothing for it to collide with.

At 71, it costs 24%, and Social Security is the reason. When IRA income lands on top of benefits, you pay tax on the IRA money and you also force up to 85% of your Social Security to become taxable. Their base income at 71 is $39,000. With the conversion, reported income jumps to $200,000. A $100,000 conversion raised their taxable line by $160,000.

At 63 and at 65 they sat in the same 12% bracket, and one year cost 30% while the other cost 11%. The collision sets the price. The tax table just provides the cover story.

Two cliffs that aren't on the bracket table

The ACA cliff is one: go $1 over the limit and the whole subsidy vanishes. The other starts at 65 with Medicare IRMAA surcharges. Once a couple's income crosses $218,000, their Part B and Part D premiums jump, adding roughly $2,300 in surcharges two years later.

For a couple over 65, that Medicare line sits nearly $29,000 below the top of the 22% bracket. Fill the 22% bracket to the top and you cross the Medicare cliff without realizing it.

The five-year plan and who collects

The full plan converts $100,000 a year for five years, from 65 through 69. Federal tax starts at $11,300 in year one and creeps to $11,800 by year five. Moving $500,000 out of the traditional IRA costs about $58,000, or 11.5 cents on the dollar.

The RMD at 75 drops from $92,000 to $62,000. Lifetime federal income tax falls by $148,000. Lifetime Medicare premiums drop by $30,000 because their income stays below the IRMAA surcharges. By 92, after all taxes, the family is ahead by just under $300,000, and that assumes tax rates stay flat for 30 years. It works because they paid the tax in five years with zero wages, zero Social Security since they claimed at 70, and zero RMDs. Once the money hit the Roth, it grew tax-free.

The biggest payoff arrives when the family is most vulnerable. Without any conversion, at 82 both spouses are alive, their income is $207,000, federal tax is $26,400 and Medicare costs $4,900. At 83 one spouse passes away and the survivor files single. Income drops to $182,000, yet federal tax rises to $30,700, an increase of $4,300, and Medicare premiums jump to $7,100. The brackets and the standard deduction shrink by half, and so do the Medicare thresholds. The RMDs keep coming, now landing on one person's return. Of the $177,000 in direct tax and Medicare savings this plan produced, $168,000 came after one spouse had died.

When the strategy breaks

This is powerful, and it isn't universal. If your tax rate when you convert matches your rate when you withdraw later, there's no arbitrage to capture. If you don't have cash outside the IRA to pay the tax, you have to pull extra from the IRA to pay the IRS, and that wrecks the math. If your heirs are in a lower bracket than you, converting means prepaying at your higher rate to spare them a rate they'd never hit. Every conversion starts its own five-year clock, and pulling converted funds out early can bring a 10% penalty if you're under 59½. And converting only because you expect tax rates to rise is risky. Future increases often come from broadening the tax base instead of raising top bracket rates.

If you're still working, your low-tax window sits somewhere ahead of you. It opens the year your paycheck stops and closes the year mandatory income switches on. For this couple it ran from 65 to 69. It only exists if you can live inside it without draining pre-tax accounts for basic expenses, which takes cash flow from outside the traditional IRA, like a taxable brokerage account, Roth contributions or rental income.

That's the setup I use. My rental income covers my baseline living expenses, so I don't touch my retirement accounts to pay the bills, and that keeps the window open. While a paycheck is still coming in, watch your taxable brokerage account and your Roth cash as closely as your 401(k). Every dollar you build outside the 401(k) buys a cheaper conversion window later.