My old employer was bought by another company. Where did my 401(k) go?

By Kaz · Published 6 October 2026 · How this site checks figures

Summary

It is in one of three places, and the IRS lists all three: still in the same plan with the buyer as the new sponsor, inside the buyer's own plan after a merger, or out of the plan altogether because one of the companies terminated it and paid the balances out. The plan's annual Form 5500 filings show which happened, because a filing has to name any plan the assets were transferred to, and the last filing of a plan that ended is marked as its final return. If many people lost their jobs around the sale, look at your vesting too: a turnover rate of 20% or more in a plan year creates a presumption of partial termination, and in a partial termination everyone who was let go must be 100% vested.

Which of the three happened

Following an old 401(k) after the employer was sold

Does the plan's latest Form 5500 still list the same plan, with a new sponsor name?

Yes → The plan continued; the new sponsor's administrator holds your account

No → Check the last filing on record

Is the last filing marked as the final return, with assets transferred to another plan?

Yes → Merged; look up the plan named on the transfer line

No → Check whether a termination was adopted

Does the final filing say a resolution to terminate was adopted?

Yes → Terminated; the money was paid out, rolled to an IRA in your name, or sent on

No → Not clear yet; ask the buyer's HR or the DOL's Benefits Advisors

How to read the filings, not a guarantee of where an account is. Filing lines change between form versions.

Source: IRS, Retirement topics: Employer merges with another company; DOL, 2025 Form 5500-SF

The 2025 Form 5500-SF, the short form most small plans file, has the lines you need. Line B has a box for "the final return/report." Line 13a asks, "Has a resolution to terminate the plan been adopted in any plan year?" Line 13c says, "If, during this plan year, any assets or liabilities were transferred from this plan to another plan(s), identify the plan(s)." Large plans file the full Form 5500 with schedules, which ask the same questions under different line numbers. Every filing is searchable for free on the DOL's EFAST2 site; the search order from your own files to the federal databases is in how to find an old 401(k).

Search under the old company's name first, then under the buyer's. A merged plan stops filing under the old name, and your account lives on inside a plan with a different name, number and sponsor.

If the plan continued or merged

The account didn't change hands in any way you had to approve. When a plan keeps going under the buyer, the IRS says the law requires "the new sponsor notify the plan's participants of the new plan sponsor's name and address." The notice goes to the address in the plan's records, which is out of date for anyone who moved after leaving and never told the plan.

After a merger the money sits in the receiving plan's funds, with that plan's expense ratios, not the ones on your last statement from the old plan. What to look for on the fee disclosure shows where the new charges appear once you find the account.

If the plan was terminated

Termination has two consequences the IRS spells out. Every participant becomes 100% vested in the account balance. The assets are paid out "as soon as administratively feasible (generally, within one year)." If you didn't answer the distribution notice, a small balance may have been moved into an IRA in your name; automatic rollovers of small balances covers who holds those IRAs and what they charge. When the company itself disappeared and nobody finished the job, what happens when an employer goes bankrupt covers the DOL's Abandoned Plan Program.

The vesting point people miss

Selling a company often comes with layoffs, and layoffs can trigger a partial termination of the old plan even when nobody terminated it. The IRS's partial termination page cites Revenue Ruling 2007-43: "a 20% or greater turnover rate in the applicable period creates a rebuttable presumption that a partial termination occurred." When it does, the participants who left during that period "must be fully vested in their account balance."

The turnover rate counts employer-initiated severances, which the ruling says includes any departure except death, disability or retirement at normal retirement age, even when "caused by an event outside of the employer's control." It counts vested and unvested participants alike. Example, with the IRS formula: 400 participants at the start of the plan year, 50 who joined during it, and 120 let go by the employer.

120 ÷ (400 + 50) = 26.7%

That's above 20%, so a partial termination is presumed, and the 120 who were let go are presumed fully vested. If one of them had $6,000 of unvested match forfeited when they left, the presumption is the ground for asking for it back.

The ruling has an exception that matters in a sale. Employees who moved to the buyer's controlled group aren't counted as severed "if those employees continue to be covered by a plan that is a continuation of the plan under which they were previously covered." So a sale where everyone transfers with their plan intact may produce no partial termination, while a sale where the buyer keeps half the staff may. The period is usually one plan year, longer for "a series of related severances." How vesting works on employer money explains what the forfeited amount would have been.

Ask the plan administrator in writing whether the plan year of the sale was reviewed for a partial termination, and what the turnover rate was. If the account is now with a provider that charges more than you'd pay elsewhere, the fee calculator puts a number on staying.

Sources

Written by Kaz, an independent publisher.
Corrections: the contact form.