How to Convert a 401(k) to a Roth IRA Without Taxes

To convert money from a 401(k) to a Roth IRA without owing federal income tax, you can only move dollars that were already taxed before they entered the plan: designated Roth 401(k) contributions and voluntary after-tax contributions. Pre-tax deferrals and employer matching contributions are taxable when converted, and there is no workaround for that. The strategy that produces the largest tax-free transfers, often called the mega backdoor Roth, uses the after-tax bucket combined with a specific IRS-approved method for separating your after-tax principal from its taxable earnings.

Which 401(k) Dollars Can Move Tax-Free

A 401(k) balance holds up to three separate types of money, and each follows its own rule on the way out.

Pre-Tax Deferrals and Employer Match

Traditional pre-tax deferrals were never taxed going in, so the IRS collects when they come out. Employer matching contributions sit in the same category, whether your own deferrals were traditional or Roth.¹ Converting these dollars adds the full converted amount to your taxable income for the year. If tax-free is the goal, this bucket doesn’t get you there.

One exception is worth flagging. Under SECURE 2.0, an employer can now deposit its match directly into a designated Roth account if the plan has adopted the feature and you elect Roth treatment. You have to be fully vested in the match to make the election, and the amount is included in your taxable income for the year it’s contributed.² Once inside your Roth account, that match rolls to a Roth IRA the same way your own Roth deferrals do. Not every plan offers this yet.

Designated Roth 401(k) Contributions

If you elected Roth treatment for your own deferrals, those contributions were taxed on your paycheck.³ Rolling designated Roth 401(k) money into a Roth IRA is a straight tax-free transfer. This is the simplest tax-free path, but it only covers what you actually designated as Roth while employed.

Voluntary After-Tax Contributions

This is the bucket most people miss. After-tax contributions are dollars you put into the plan beyond your regular elective deferrals, funded with money you already paid tax on. They live in a separate after-tax account inside the plan, not in your designated Roth account. Because the principal was already taxed, only the investment earnings on those contributions are taxable when converted. The principal itself rolls into a Roth IRA free of any additional tax.⁴

Splitting After-Tax Principal From Pre-Tax Earnings

After-tax contributions accumulate earnings while they sit in the plan, and those earnings are pre-tax money. You cannot cherry-pick just the principal at distribution. What you can do, under IRS Notice 2014-54, is direct the plan administrator to send the pre-tax portion (the earnings) to a traditional IRA and the after-tax portion (your principal) to a Roth IRA in a single, simultaneous distribution.⁴

The IRS guidance gives a clean example. A participant with $80,000 of pre-tax money and $20,000 of after-tax contributions can direct the $80,000 to a traditional IRA and the $20,000 to a Roth IRA. The entire Roth IRA portion is after-tax money, so no tax is owed on that piece. Both rollovers must go out as part of the same distribution event.

The practical implication is timing. The longer after-tax dollars sit in the plan, the more taxable earnings pile up alongside them. If your plan offers automatic in-plan Roth conversions or frequent in-service withdrawals, use them. Some plans convert after-tax contributions to Roth after every payroll cycle, which keeps taxable earnings close to zero.

The Mega Backdoor Roth

The mega backdoor Roth combines existing rules to move large amounts into a Roth IRA each year with little or no tax. You max out your regular 401(k) deferrals, add after-tax contributions up to the plan’s total contribution ceiling, and roll those after-tax dollars into a Roth IRA before they accumulate meaningful earnings.

For 2026, the total 415(c) limit for all contributions to a defined contribution plan — your deferrals, employer match, and after-tax contributions combined — is $72,000.⁵ The elective deferral limit is $24,500, with an $8,000 catch-up at age 50 and older.⁶ Whatever is left after subtracting your deferrals and your employer’s match from the $72,000 ceiling is your after-tax room. If you defer $24,500 and your employer contributes $10,000, that leaves $37,500 for after-tax contributions that can eventually land in a Roth IRA.

Two plan features have to be in place. First, the plan must allow voluntary after-tax contributions. Second, it must permit either in-service withdrawals of those after-tax funds or automatic in-plan Roth conversions. Without both, the money stays locked in the after-tax bucket until you leave the employer. Check your Summary Plan Description or ask the plan administrator before committing.

Income is not a barrier here. Congress removed the income limit for Roth conversions starting in 2010, and none has been reinstated.⁷ You can convert any amount from a 401(k) to a Roth IRA regardless of what you earn, which is precisely why the mega backdoor Roth appeals to people whose income disqualifies them from contributing to a Roth IRA directly.

The Pro-Rata Trap With Existing Traditional IRAs

Rolling after-tax 401(k) money directly to a Roth IRA sidesteps a common pitfall. Under the pro-rata rule, the IRS treats all of your traditional IRAs as a single pool when calculating how much of any conversion is taxable.⁸ If you park $20,000 of after-tax 401(k) contributions in a traditional IRA that already holds $180,000 of pre-tax money and then try to convert just the $20,000 piece, the IRS calculates the taxable portion based on the ratio of pre-tax to total IRA funds. In that example, the conversion would be 90% taxable.

The fix is to send after-tax 401(k) contributions straight to the Roth IRA, and send the pre-tax earnings piece to a traditional IRA or back into your employer’s 401(k). If you already hold large traditional IRA balances, consider rolling them into your current employer’s 401(k), if the plan accepts incoming rollovers, before you attempt any conversion.

Executing the Rollover

Use a Direct Rollover

A direct rollover, sometimes called a trustee-to-trustee transfer, sends the money straight from the plan administrator to your Roth IRA custodian. You never touch it. That is the method you want. It avoids the mandatory 20% federal income tax withholding that applies when a retirement plan distribution is made payable to you personally.⁹ Your plan administrator will ask for a Direct Rollover Election Form listing the receiving Roth IRA’s account number, the custodian’s legal name, and either a mailing address or electronic transfer instructions. Electronic wires generally settle in three to five business days.

Why the Indirect Rollover Is Risky

If the plan cuts a check payable to you, you have exactly 60 days to deposit the full amount into the Roth IRA.⁹ Miss the deadline and the whole distribution becomes taxable, potentially with a 10% early withdrawal penalty. The plan is also required to withhold 20% for federal taxes before writing the check. To roll over the full pre-withholding amount, you have to make up the withheld 20% out of pocket and deposit it with the check. You’ll get the withholding back as a tax refund, but you’re floating the cash in the meantime.

What to Have Ready

Ask the plan administrator for a current account statement showing the split between pre-tax, Roth, and after-tax balances. The after-tax figure, sometimes labeled “cost basis,” is the number that drives your tax-free conversion. Get a copy of the Summary Plan Description to confirm the plan allows after-tax contributions and in-service distributions. Open the Roth IRA at your chosen custodian before you initiate anything; the receiving account has to exist first.

After the Conversion

The Five-Year Clock

Getting money into a Roth IRA tax-free doesn’t mean you can pull it out immediately without consequences. Each conversion starts its own five-year clock. If you withdraw converted amounts before five years have passed and you are under age 59½, the IRS imposes a 10% early withdrawal penalty on the portion of the conversion that was included in your taxable income.¹⁰ For a tax-free conversion of after-tax contributions, no principal was included in income, so the penalty applies only to whatever taxable earnings came along with the conversion. Once you reach 59½, the penalty no longer applies whether or not the five years have elapsed.

Roth IRA earnings follow a separate rule. For a distribution of earnings to be fully tax-free and penalty-free, both the five-year aging requirement on the Roth IRA itself and the 59½ threshold must be met.⁷ The account-level clock starts on January 1 of the tax year you first funded any Roth IRA, so if you’ve held one for years, new conversions benefit from that earlier start date for the account rule.

Report the Conversion Even When Nothing Is Taxable

A tax-free conversion still has to be reported. Skipping the paperwork creates audit risk and can lead the IRS to treat your rollover as a taxable distribution.

Your plan administrator sends you and the IRS a Form 1099-R. Box 1 shows the total distributed, Box 2a shows the taxable portion, and Box 7 carries a distribution code. Code G indicates a direct rollover to a qualified plan or IRA.¹¹ For a fully tax-free conversion, Box 2a should be zero or close to it. Keep the form permanently.

File Form 8606 with your tax return to track the after-tax basis in your Roth IRA.¹² The IRS doesn’t track your basis for you, and losing the documentation can leave you unable to prove later that part of your balance was already taxed.¹³

On Form 1040, report the distribution on line 5a using the Box 1 amount from your 1099-R. If everything was rolled over and nothing is taxable, enter zero on line 5b and check the rollover box on line 5c.¹⁴ That zero is what tells the IRS you moved the money rather than spent it.

You Cannot Undo the Conversion

Before 2018, you could reverse a Roth conversion through a process called recharacterization. The Tax Cuts and Jobs Act eliminated that option. Once you convert, the transaction is permanent. If you convert a large pre-tax amount and your income turns out higher than expected, you’re stuck with the tax bill. That permanence is one more reason to concentrate tax-free conversions on after-tax and Roth 401(k) dollars, where no taxable income shows up in the first place.

1
Office of the Law Revision Counsel. 26 USC 402 – Taxability of Beneficiary of Employees Trust
2
Internal Revenue Service. SECURE 2.0 Act Changes Affect How Businesses Complete Forms W-2
3
Office of the Law Revision Counsel. 26 USC 402A – Optional Treatment of Elective Deferrals as Roth Contributions
4
Internal Revenue Service. Guidance on Allocation of After-Tax Amounts to Rollovers (Notice 2014-54)
5
Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs (Notice 2025-67)
6
Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
7
Office of the Law Revision Counsel. 26 USC 408A – Roth IRAs
8
Office of the Law Revision Counsel. 26 USC 408 – Individual Retirement Accounts
9
Internal Revenue Service. Rollovers of Retirement Plan and IRA Distributions
10
Internal Revenue Service. Retirement Topics – Exceptions to Tax on Early Distributions
11
Internal Revenue Service. Form 1099-R – Distributions From Pensions, Annuities, Retirement or Profit-Sharing Plans, IRAs, Insurance Contracts
12
Internal Revenue Service. About Form 8606 – Nondeductible IRAs
13
Internal Revenue Service. Instructions for Form 8606 – Nondeductible IRAs
14
Internal Revenue Service. Instructions for Form 1040 (2025)