You can roll a Traditional IRA into a 401k if the employer’s plan agrees to accept the money, and federal law permits the move for pre-tax dollars only. This is sometimes called a reverse rollover, and done correctly through a direct trustee-to-trustee transfer, it creates no tax bill. Done carelessly, it can cost you income tax on the full balance plus a 10% early withdrawal penalty. The rules are specific, and a few of them have sharp edges.
Why Move IRA Money Into a 401k
Most retirement advice runs the other direction, so it helps to know what you’re gaining by going backward.
ERISA-qualified 401k plans have unlimited creditor protection in bankruptcy. Traditional IRAs are shielded only up to roughly $1,711,975 under the federal bankruptcy exemption for 2026, and outside bankruptcy the protection depends on your state. If you work in a field with real litigation exposure, consolidating IRA money into a 401k closes that gap.
The Rule of 55 is the second reason. Leave your job during or after the year you turn 55 and you can pull money from that employer’s 401k without the 10% early withdrawal penalty, years before age 59½. Public safety employees can use age 50. The exception does not exist for IRAs, including rollover IRAs, so money sitting in an IRA can’t be reached the same way.
For high earners, the biggest driver is the backdoor Roth conversion. The IRS treats all your Traditional, SEP, and SIMPLE IRAs as one pool for pro-rata purposes when you convert to a Roth. Any pre-tax dollars in that pool make part of every conversion taxable, even if you meant to convert only nondeductible contributions. 401k balances are excluded from the pro-rata formula, so moving the pre-tax IRA money into a 401k before year-end clears the path to a tax-free conversion of your remaining after-tax basis.
Two smaller reasons round it out. IRAs don’t allow loans; a 401k can let you borrow up to the lesser of 50% of your vested balance or $50,000, and a larger balance means a larger potential loan. And many 401k plans offer institutional share classes with lower expense ratios than retail funds in an IRA, though some small-employer plans carry administrative fees heavy enough to erase that advantage. Compare the all-in cost before you move anything.
What You’re Allowed to Roll Over
Federal law permits the transfer, but the receiving plan is not required to accept it. The IRS is clear that a plan can refuse rollover contributions from IRAs or other plans. Before you start, find your Summary Plan Description, which lives on your plan provider’s website or with HR, and look for the section on rollover contributions. Some plans accept rollovers from any Traditional IRA; others limit incoming money to distributions from prior employer plans. If the language is ambiguous, call the plan administrator.
Only pre-tax Traditional IRA money is eligible. Roth IRAs cannot be rolled into a 401k at all; the IRS rollover chart does not permit it. If your Traditional IRA holds nondeductible contributions, that after-tax basis also cannot go into the 401k, because the statute limits rollovers to amounts that would be includible in gross income. Say you have $100,000 in a Traditional IRA with $30,000 of nondeductible basis. Only the $70,000 pre-tax portion qualifies for the rollover; the $30,000 stays in the IRA.
If the account is a SIMPLE IRA, you must wait at least two years from the date you first participated in the SIMPLE plan before rolling those funds to a 401k. Breaking this rule triggers income tax on the full amount plus a 25% additional tax, which is steeper than the usual 10% early withdrawal penalty.
Self-employed workers with a solo 401k can accept rollovers from Traditional, SEP, and SIMPLE IRAs under the same rules. There’s no dollar cap on how much you can move, and you can roll over all or part of the IRA balance.
Direct Rollover Versus Indirect Rollover
How you move the money matters as much as whether you’re allowed to.
In a direct rollover, your IRA custodian sends the funds straight to the 401k plan’s trustee. You never touch the money. Nothing is withheld, no deadline runs, and the transaction is reported with distribution code G on Form 1099-R, telling the IRS the amount is non-taxable. Use this method unless your custodian genuinely cannot accommodate it.
In an indirect rollover, the IRA custodian sends the money to you. You then have 60 calendar days to deposit it into the 401k. Miss the deadline and the IRS treats the whole amount as a taxable distribution, with a 10% penalty on top if you’re under 59½. Default withholding on an IRA distribution to you is 10%, and you can elect out of it, which is different from employer-plan distributions where 20% withholding is mandatory. If your custodian does withhold, you’ll need to replace the withheld amount from other funds to roll over the full balance; whatever you don’t replace becomes a taxable distribution.
If you miss the 60-day window for a qualifying reason, Revenue Procedure 2020-46 lets you self-certify the late rollover in writing to the accepting plan, which can rely on the certification absent reason to doubt it. The list of qualifying reasons is specific (hospitalization, natural disaster, financial institution error, and a handful of others), and if the IRS later determines the certification wasn’t valid, the distribution becomes taxable retroactively.
How to Complete the Transfer
Once you’ve confirmed the plan accepts incoming rollovers and you’ve chosen the direct method, the sequence is short.
Get the plan’s trustee name, the mailing address for the plan administrator, and your participant account number from HR or the provider’s site. Request a Rollover Contribution Form from the 401k plan; the form asks you to identify the source of the funds, confirm they’re from a qualifying account, and authorize the deposit. Submit your most recent IRA statement with it so the plan can verify the source.
Then contact your IRA custodian to initiate the distribution. For a direct rollover, the check must be payable to the 401k plan’s trustee, followed by “FBO” (for benefit of) and your full legal name. A payee line like “Fidelity Management Trust Company FBO Jane Smith” is the pattern. Getting this wrong is the single most common reason checks get bounced back, adding weeks. Some IRA custodians can send funds by electronic wire for a fee, typically $25 to $75.
If a paper check is issued, mail it with the Rollover Contribution Form to the plan administrator using a trackable service. When the 401k provider processes the deposit, they’ll send confirmation showing the amount received and where it was invested. Read that notice the day it arrives. Errors in the amount or fund allocation are easier to fix in the first few days than later.
Some IRA custodians require a Medallion Signature Guarantee on the paperwork, especially for larger balances. This is a stamp from a participating bank or brokerage that verifies your identity and signature. Ask your custodian in advance; if you need one, you’ll have to visit a branch of a participating institution.
Timing a Reverse Rollover for a Backdoor Roth
If the point of the rollover is to enable a clean backdoor Roth conversion, the calendar drives everything. The pro-rata calculation uses your combined Traditional, SEP, and SIMPLE IRA balance on December 31 of the conversion year, not the date of conversion. The pre-tax money has to be out of your IRAs and into the 401k by that date.
The math works like this. If you had $200,000 of pre-tax IRA money and a $7,000 nondeductible contribution, and you roll the $200,000 into your 401k before year-end, your December 31 IRA balance is just the $7,000 of after-tax basis. Convert that $7,000 to a Roth and you owe zero tax on the conversion. Leave the $200,000 in the IRA and nearly all of the conversion becomes taxable.
Because a rollover can take weeks between paperwork, mailing, and processing, starting in November is cutting it dangerously close. If a backdoor Roth is the goal, begin earlier in the year.
Reporting the Rollover on Your Taxes
A clean direct rollover generates little tax paperwork, but it still gets reported.
Your IRA custodian issues Form 1099-R for the year the distribution occurs. On a direct rollover, box 7 shows distribution code G, box 2a (taxable amount) should be $0, and box 4 (federal tax withheld) should be $0.
On Form 1040, report the distribution on line 4a with the full amount, put $0 on line 4b, and write “ROLLOVER” next to it. That tells the IRS the money moved between qualified accounts.
Your 401k provider files Form 5498 to report the incoming contribution, usually by the following May. You don’t attach it to your return; keep it with your records as proof the money landed in a qualified plan.
If your IRA held nondeductible contributions and you rolled over only the pre-tax portion, file Form 8606 with your return to update your basis tracking. Skipping Form 8606 can lead to double taxation on money that was already taxed once.
Mistakes That Turn a Rollover Into a Tax Bill
- Missing the 60-day window on an indirect rollover. The whole distribution becomes taxable income, with a 10% penalty added if you’re under 59½. Revenue Procedure 2020-46 self-certification can rescue you, but only for the specific qualifying reasons.
- Rolling over nondeductible basis. A 401k accepts only pre-tax dollars. Sending your whole IRA balance without separating out the basis either gets rejected by the plan or wipes out your basis records.
- Forgetting the SIMPLE IRA two-year rule. Moving SIMPLE money to a 401k before the two-year mark triggers a 25% penalty instead of the usual 10%.
- Wrong payee on the check. If the check is made out to you rather than the 401k trustee, the transaction becomes an indirect rollover and the 60-day clock starts, even if you meant to do a direct transfer.
- Not reporting the rollover on your return. The rollover isn’t taxable, but it still has to appear on Form 1040. When the IRS sees a 1099-R with no matching rollover reported, expect a letter proposing tax on the full amount.