When you leave a job, your 401(k) doesn’t leave with you. It sits at the old employer’s recordkeeper under your name, and unless you do something about it, it can sit there for decades. Plenty of people are fine with that until they realize they can’t remember which company held the account at the job before last.
The scale of this is larger than most people would guess. A study by Capitalize, which specializes in tracking down old workplace accounts, estimates there are roughly 31.9 million forgotten or left-behind 401(k) accounts in the United States holding about $2.13 trillion, or around a quarter of all 401(k) plan assets. The average forgotten balance had risen to $66,691 by March 2026, up 18% from $56,616 in May 2023.
Understanding how a rollover works is what keeps your money from joining that pile, and more importantly, keeps you from accidentally handing a fifth of it to the IRS.
Your Options When You Leave a Job
Four things can happen to a 401(k) after you separate from an employer. You can leave it where it is, assuming the balance clears the plan’s minimum. You can roll it into your new employer’s plan, if that plan accepts incoming rollovers, and most do. You can roll it into an individual retirement account you control. Or you can cash it out, which triggers income tax on the full amount plus a 10% early distribution penalty if you’re under 59½.
The first three are all rollovers of one kind or another, and they’re not taxable events when done correctly. The phrase “when done correctly” is carrying a lot of weight in that sentence.
Direct Rollover: The Money Never Touches You
A direct rollover, sometimes called a trustee-to-trustee transfer, means your old plan sends the money straight to the receiving account. The check, if there is a physical check, is made payable to the new custodian for your benefit, not to you personally. Some plans mail it to your house anyway, which confuses people. Look at the payee line. If it says something like “Fidelity Management Trust Company FBO Jane Smith,” it’s a direct rollover and you’re just the courier.
Nothing is withheld for taxes. There’s no deadline hanging over you. The transaction gets reported on a Form 1099-R with a distribution code showing it was a direct rollover, and you report it on your return as a nontaxable event. This is the version you want in nearly every case.
Indirect Rollover and the 20% Withholding Trap
An indirect rollover is what happens when the distribution is made payable to you. You get the money, and then you have to put it into another retirement account yourself.
Here’s where it goes wrong. When an employer plan pays a rollover-eligible distribution directly to a participant, federal law requires the plan to withhold 20% for taxes. This is mandatory. You cannot opt out, and asking nicely does not help.
Say your balance is $50,000 and you request a distribution payable to yourself. The plan withholds $10,000 and sends you a check for $40,000. To complete a full rollover and owe nothing, you have to deposit $50,000 into the new account, not $40,000. The missing $10,000 has to come from your own pocket, meaning a savings account or something else liquid, and you get it back as a credit when you file your return the following spring.
If you only deposit the $40,000 you received, the other $10,000 is treated as a taxable distribution. You’ll owe ordinary income tax on it, and if you’re under 59½, a 10% penalty on top. A rollover you thought was free ends up costing several thousand dollars, entirely because of which name went on the check.
The 60-Day Clock
The other half of the indirect rollover problem is timing. Once you receive the money, you have 60 days to deposit it into an eligible retirement account. Miss the window and the entire distribution becomes taxable income for that year, plus the early withdrawal penalty if it applies. Fidelity’s explanation of the 60-day rollover rule covers the mechanics and the narrow set of circumstances in which the IRS will waive a missed deadline, which generally requires a documented reason like a hospitalization or a financial institution’s error.
Sixty days sounds like plenty of time. It is, right up until the check arrives while you’re moving, or the new account isn’t open yet because the paperwork needs a signature guarantee, or you decide to park the money for a few weeks and lose track. The clock runs on calendar days and starts when you receive the funds.
There’s a related rule people confuse with this one. The limit of one rollover per 12-month period applies only to IRA-to-IRA indirect rollovers. It does not apply to direct rollovers or to moving money out of a workplace plan. The IRS rollover guidance lays out which transfers count against that limit.
Small Balances Can Be Moved Without You
If your balance is small, the plan may not wait for you to decide. Under SECURE 2.0, a plan can force out a former employee’s account of $7,000 or less without consent, up from the old $5,000 threshold. You get a notice and a chance to choose where the money goes, but if you ignore it, the plan can roll the balance into a default Safe Harbor IRA in your name, typically invested in something conservative like a money market fund.
That’s how a lot of accounts end up forgotten. The address on file is three moves old, the notice never reaches you, and the money lands at a custodian you’ve never heard of.
The Department of Labor has been building out an auto-portability framework meant to fix this, where those small Safe Harbor IRA balances automatically follow you into your next employer’s plan once you enroll. It’s gaining real traction in 2026, though as CNBC has reported, the network currently moves traditional pre-tax money only. Roth balances don’t ride along, because Roth IRA money cannot be rolled into a 401(k).
If You’ve Already Lost One
Start with the Department of Labor’s Retirement Savings Lost and Found, a national database created under SECURE 2.0 and launched at the end of 2024, which lets you search for plans that reported benefits owed to you. The National Registry of Unclaimed Retirement Benefits is a second free search, using your Social Security number. Old Form 5500 filings on the DOL site will tell you which recordkeeper administered a former employer’s plan, which is useful when the company has since been acquired or shut down. Your state’s unclaimed property office is worth a check as well, since abandoned accounts eventually escheat.
If you do find one, request a direct rollover. Every time. The paperwork takes an extra week and saves you the entire problem described above.