Nine Januarys of Conversions, and $610,000 the IRS Can't Touch

A retiree who made after-tax contributions to his 401(k) for nine years and converted the money to Roth every January retired at 62 with $610,000 that will never face federal income tax again, according to 24/7 Wall St.

There are three ways money can go into a 401(k), and most savers only ever use one of them. Pre-tax deferrals are the default. Roth deferrals are the increasingly common alternative. The third — plain after-tax contributions, distinct from Roth — sits in the plan document, unused, at most companies that offer it at all.

One retiree used it. According to 24/7 Wall St, he made after-tax contributions for nine consecutive years and converted the balance to Roth every January. He retired at 62 with $610,000 that federal income tax will never reach again.

What the third bucket actually is

The after-tax bucket is money you put into the plan with dollars that have already been taxed — same as a Roth contribution in that respect. The difference is what happens to the growth. In a Roth account, contributions and earnings both come out tax-free in retirement. In a plain after-tax account, only your original contributions come out tax-free; the investment gains are taxed as ordinary income when withdrawn.

That makes the after-tax bucket a mediocre place to park money on its own. Its value is as a staging area. Move that money into a Roth account and the earnings clock resets: from the conversion forward, growth is tax-free rather than tax-deferred. This is the manoeuvre commonly called the mega backdoor Roth, and the annual January conversion in this case is the operative step. Convert quickly, before the after-tax dollars have generated much in the way of gains, and the conversion itself triggers little or no tax.

The word "mega" refers to the size of the opening. Elective deferrals — the pre-tax or Roth money you choose to have withheld from your paycheck — face one annual limit. The after-tax bucket lives under a separate, much larger overall cap that counts employee deferrals, employer match and after-tax contributions together. The gap between the two limits is the room the strategy exploits. The IRS sets both numbers and adjusts them for inflation; check the current year's figures before assuming any particular amount of headroom, because the arithmetic changes annually and your employer's match eats into it.

Why most people can't copy this

The strategy is not blocked by tax law. It is blocked by plan documents. Two features have to be present:

• After-tax contributions must be permitted. Many 401(k) plans simply don't offer the bucket. If yours doesn't, there is nothing to convert and no workaround inside the plan.
• The plan must allow either in-plan Roth conversions or in-service withdrawals. The first moves the after-tax money to a Roth 401(k) sub-account without leaving the plan. The second lets you roll it out to a Roth IRA while still employed. Without one of these, the after-tax money is trapped until you separate from the employer, and years of earnings accumulate in a taxable-on-withdrawal state.

A third obstacle is less visible: nondiscrimination testing. After-tax contributions are subject to the ACP test, which compares what highly compensated employees put in against what everyone else does. When only a handful of senior earners use the bucket, plans can fail the test and refund contributions after the fact. Some employers sidestep this with a safe harbor design; others cap after-tax contributions at a low percentage of pay precisely to stay compliant. Either way, the headline limit is often not what an individual employee can actually reach.

The pro-rata trap and how the January timing avoids it

Pro-rata rules are where this strategy usually goes wrong. Broadly, when you take a distribution from an account holding both taxed and untaxed money, you cannot cherry-pick the taxed portion. The distribution comes out proportionally, and the untaxed slice is income.

Inside a 401(k), the after-tax bucket is tracked separately from pre-tax deferrals, which is why an in-plan conversion of just the after-tax sub-account is generally clean. But the earnings on those after-tax dollars are pre-tax money sitting in the same sub-account, and they do get pulled in. That is the entire logic of converting every January rather than every decade: minimise the earnings that have accrued, minimise the taxable portion of the conversion. Some plans go further and offer automatic conversion, sweeping after-tax contributions to Roth with each payroll cycle, which reduces the taxable earnings to near zero.

Anyone rolling after-tax 401(k) money out to a Roth IRA rather than converting in-plan faces a separate pro-rata calculation involving all their traditional IRA balances. That version needs planning, and often a conversation with a tax professional, before the first dollar moves.

What $610,000 of tax-free money is worth in retirement

The number itself is only half the story. A Roth balance behaves differently from a traditional one in ways that matter after 62.

It generates no taxable income when drawn, which keeps a retiree's adjusted gross income lower — and AGI is the input that determines how much of Social Security is taxable and which Medicare premium bracket applies. It is not subject to required minimum distributions during the owner's lifetime under current rules, so the money can compound untouched while other accounts are drained on the government's schedule. And it passes to heirs without an income tax bill attached, though the ten-year distribution window for most non-spouse beneficiaries still applies.

The practical use is flexibility. A retiree with both traditional and Roth balances can choose, each year, how much taxable income to recognise — filling up a low bracket from the pre-tax account and topping off spending from the Roth. That control is difficult to buy any other way.

The checks worth running this week

Start with the summary plan description, not the enrollment portal. It will say whether after-tax contributions are allowed and whether in-plan conversions or in-service withdrawals are available. If the plan permits after-tax money but not conversions, ask HR whether automatic in-plan Roth conversion can be added — it is a common amendment and costs the employer little.

Then check whether you are maxing the ordinary deferral first. The after-tax bucket is the last stop, not the first: elective deferrals, full employer match, HSA if eligible, then after-tax. Contributing after-tax dollars while leaving match on the table is backwards.

Finally, set the conversion as a standing instruction rather than an annual chore. The retiree in this account did it every January for nine years. The discipline, more than the tax code, is what produced the balance.

Markets, for context on the day this was reported, were higher: the S&P 500 tracker (NYSEARCA: SPY) traded at $766.39, up 0.50%, as of 17:07 GMT on 21 August 2026, with the Nasdaq 100 fund at $713.94 and the Dow 30 fund at $531.13.

Key facts

• Tax-free balance at retirement: $610,000
• Years of after-tax contributions: Nine, converted each January
• Retirement age: 62
• S&P 500 ETF (NYSEARCA: SPY): $766.39, +0.50%, as of 17:07 GMT 21 Aug 2026

Frequently asked questions

What is the 'third bucket' in a 401(k)?

A 401(k) can hold pre-tax deferrals, Roth deferrals and plain after-tax contributions. The third — after-tax, not Roth — is funded with already-taxed dollars, but unlike Roth money its investment earnings are taxed as ordinary income on withdrawal. Most plans either don't offer it or employees never notice it exists in the plan document.

Why convert the after-tax money every January?

Converting after-tax dollars to Roth is generally tax-free on the contributions themselves, but any investment earnings that have accrued in the after-tax bucket are taxable at conversion. Converting promptly and frequently keeps those earnings small, so the tax bill on each conversion stays near zero. The retiree described did it annually for nine straight years.

Does every 401(k) plan allow this?

No. The plan must permit after-tax contributions and must also allow either in-plan Roth conversions or in-service withdrawals. Many plans offer neither. Check the summary plan description rather than the enrollment website, and ask HR directly whether automatic in-plan Roth conversion can be added to the plan.

How much can be contributed after-tax?

Elective deferrals face one annual IRS limit; the after-tax bucket falls under a separate, larger overall cap covering employee deferrals, employer match and after-tax money combined. The usable room is the gap between the two, reduced by whatever the employer contributes. Both limits are inflation-adjusted annually, so verify the current year's figures.

What are the pro-rata rules and do they apply here?

Pro-rata rules prevent you from withdrawing only the already-taxed portion of a mixed account. Inside a 401(k), the after-tax sub-account is tracked separately, so an in-plan conversion is usually clean apart from accrued earnings. Rolling to a Roth IRA instead triggers a broader calculation involving all your traditional IRA balances.

How does a Roth balance help after age 62?

Withdrawals produce no taxable income, keeping adjusted gross income lower — which affects how much Social Security is taxed and which Medicare premium bracket applies. Under current rules there are no required minimum distributions during the owner's lifetime, and heirs inherit without an income tax bill, though most non-spouse beneficiaries face a ten-year withdrawal window.

Sources

• He Put After-Tax Money Into His 401(k) for Nine Years and Converted It Every January. He Retired at 62 With $610,000 the IRS Will Never Tax Again. — 24/7 Wall St

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