The Rules That Turn Leftover 401(k)s Into Dormant IRA Cash

Financial advisors keep telling savers to activate dormant IRA funds, but many of those idle balances were parked in cash by federal safe-harbor rules. As of July 2025, Capitalize and the Center for Retirement Research counted 31.9 million leftover 401(k)s holding about $2.1 trillion. A slice of that pile is later forced into IRAs built to hold still.

The usual lecture is to rebalance once a year and stop letting inflation chew cash. The quieter fact is that the law that “protects” small leftover workplace accounts is the same law that parks them in principal-preservation products, then hides those IRAs from the government’s own search tool.

31.9 Million Accounts Hold $2.1 Trillion

Capitalize’s biennial study with Boston College’s Center for Retirement Research, published September 30, 2025, put the leftover stock at 31.9 million left-behind 401(k) accounts as of July 2025. The average balance was $66,691, up 18% from $56,616 in the 2023 edition, mostly because markets lifted the funds already sitting in those plans.

Assets in the forgotten accounts rose 29% from mid-2023 to $2.1 trillion. That was almost 25% of the $9.3 trillion then held in 401(k)s, per Investment Company Institute figures Capitalize used for June 2025. The count has nearly doubled in a decade, even though quits have cooled from the 2021-2022 peak, because more workers now have a 401(k) to leave behind.

THE LEFTOVER 401(K) PILE

Job changes keep feeding the pile. Capitalize counted 3.5 million accounts left behind in 2023 and 4.0 million in 2024. Federal cuts in the first half of 2025 add a public-sector version of the same mess: left-behind Thrift Savings Plan accounts were projected to rise 14% in 2025, to 2.8 million from 2.4 million at the end of 2024, against a TSP that held almost $1 trillion and 7.2 million participants in December 2024.

A leftover 401(k) is not automatically a dead account. Many still sit in the old employer’s target-date fund and keep compounding, which is why treating every neglected workplace plan as a crisis overstates the harm. The leak starts when the balance is small enough for the plan to push it out.

The Law Parks Small Balances in Cash IRAs

When a worker leaves a job and does nothing, the old plan’s options are set by dollar thresholds, not by the saver’s age or mix. SECURE 2.0 raised the involuntary IRA rollover limit to $7,000 from $5,000 for distributions after December 31, 2023, so more small balances now leave the 401(k) without a signature.

WHERE A LEFT-BEHIND BALANCE GOES

• Under $1,000: The plan can cash the worker out and mail a check, minus withholding, to the last known address; uncashed checks later land in state unclaimed-property funds.
• $1,000 to $7,000: The plan can force a rollover into a safe harbor IRA the worker never picked, at a provider the plan chose.
• Above $7,000: The money generally stays in the old 401(k) unless the worker rolls it, cashes out, or the plan later terminates.

The Department of Labor’s automatic-rollover safe harbor, at 29 CFR 2550.404a-2, tells the fiduciary how that IRA must be invested. The written deal with the IRA provider has to put the money in a product designed to preserve principal and provide a reasonable rate of return, consistent with liquidity, and to seek to hold the dollar value equal to the amount invested.

That is a cash-like mandate, not a growth mandate. Capitalize notes that more accounts will now take this forced path after SECURE 2.0, and that those IRAs typically use conservative, cash-like vehicles whose returns trail a stock-and-bond mix. Fees on the 401(k) side already bite: ICI data cited in the same study put the median 401(k) fee at 0.75% of assets a year and the 90th percentile at 1.45%. In a worst-case run of high fees and a stale mix, Capitalize says one person could miss more than $500,000 over a career.

Rollover Cash Can Sit for Seven Years

Even a rollover the worker did choose often arrives as cash, and cash is sticky. Andy Reed, head of behavioral economics research in Vanguard’s Investment Strategy group, has spent years on that inertia. Vanguard tracked about 68,000 rollovers into its IRAs that began in 2015 through year-end 2022.

What our research showed is that it stays in cash and it stays in cash and it stays in cash. And for many investors, it stays in cash for seven years or longer, especially those who are younger, which is quite painful because they have the longest time horizon, they should have the lowest amount of cash, and those who have smaller balances.

Andy Reed, head of behavioral economics research, Vanguard Investment Strategy group, on The Long View

Reed’s team then asked hundreds of people who had rolled money or contributed and left it in cash whether they knew how the IRA was invested. Very few realized it was entirely in cash. Some meant to invest and never did. A number thought the IRA worked like a 401(k) and would invest itself. Younger savers and smaller balances, the group that should hold the least cash, were the most likely to stay parked.

Vanguard has pushed for an IRA version of the 401(k) qualified default investment alternative, so a rollover would land in a target-date fund unless the owner opted out. The firm’s analysis says putting rollover assets into a diversified default instead of cash could generate over $170 billion in extra retirement wealth each year from rollovers alone, and Reed has said the average investor would gain six figures by retirement. In 401(k)s, auto-enrollment already shows how defaults work: Reed cited participation around 90% with automatic enrollment versus about 60% when joining is voluntary.

Cash inside an IRA is not a zero yield in this rate cycle. Federal Reserve H.6 data show $750.2 billion in IRA and Keogh accounts sitting at money market funds as of August 2026. That is still a cash-like sleeve inside a $19.9 trillion IRA market, and it is a different quantity from leftover 401(k)s. It does show how much retirement money is willing to wait.

The Federal Search Tool Cannot See IRAs

Congress tried to make lost workplace plans findable. It did not close the IRA hole those plans create.

HOW THE SEARCH RULES WERE BUILT

1. December 29, 2022: Congress signs the SECURE 2.0 Act, which orders a national lost-and-found database and allows auto portability services for small leftover balances.
2. December 31, 2023: The involuntary IRA rollover ceiling rises to $7,000, so more small 401(k)s can be forced into default IRAs.
3. November 2023: The Portability Services Network, a recordkeeper clearinghouse, goes live to match those small IRAs with new workplace plans.
4. December 27, 2024: The Labor Department opens the public Retirement Savings Lost and Found to workers who verify their identity through Login.gov.
5. June 30, 2026: ICI puts total U.S. retirement assets at $51.2 trillion, with IRAs at $19.9 trillion, a year after Capitalize’s leftover-401(k) snapshot.

The Retirement Savings Lost and Found Database is free. A worker creates a Login.gov account, proves identity with a legal name, date of birth, Social Security number, and photos of an active driver’s license, then searches by Social Security number. Results list private-sector and union plans tied to that number and give plan-administrator contacts. The site does not decide eligibility, process claims, or pay benefits. Labor staff are barred by federal law from running the search for you.

The FAQ on the same site is blunt about IRAs: the website cannot help you find individual retirement accounts, or plans sponsored by government entities or certain religious organizations. It also cannot search for a deceased spouse. Some contact records come from old Form 8955-SSA filings and can list a 2005 administrator after the plan has merged. A worker without a state-issued ID cannot get in yet; passports and military IDs are promised later.

So the tool built to recover forgotten workplace money goes dark at the exact moment a small 401(k) is converted into the dormant IRA that advisors then tell people to “activate.” ICI’s September 17, 2026 release put $19.9 trillion in IRA assets as of June 30, 2026, up 9.2% from March, inside a $51.2 trillion retirement market that was 33% of U.S. household financial assets. Defined-contribution plans held $15.0 trillion, including $10.8 trillion in 401(k)s and $1.2 trillion in the TSP. The leftover-401(k) estimate is still the July 2025 Capitalize count; it is not a June 2026 restatement.

Recordkeepers Now Sweep Small IRAs to New Jobs

Auto portability is the industry’s answer to the cash-parked IRA. After a small pre-tax balance is forced into a default IRA, participating recordkeepers periodically check whether that person has enrolled in a new employer plan. If both the old plan and the new plan are in the network, the IRA can move into the new 401(k) unless the worker opts out. Roth balances are still left out of that sweep.

The Portability Services Network, owned by Alight, Fidelity, Empower, TIAA, Principal, and Vanguard, went live in November 2023 and uses Retirement Clearinghouse technology. Steve Holman of the network said in July 2026 that those six firms are 6 of the top 10 defined-contribution recordkeepers by participants, covering 63% of DC participants, 82 million workers, and more than 185,000 employer plans. Plans that have adopted the feature, he said, already represent over 7 million active participants. Fidelity’s third-quarter 2025 retirement trends put adoption at about 9,200 of its plans, roughly one third of its sponsor base.

AUTO PORTABILITY SO FAR

• Matched IRAs: Neal Ringquist, chief revenue officer of the Portability Services Network and Retirement Clearinghouse, said 31,216 IRAs had been matched and rolled into new 401(k)s as of March 2026.
• Job changes: The network’s own FAQ says 14.8 million defined-contribution participants change jobs each year, which is the flow auto portability is built to catch.
• Voluntary feature: Plan adoption is optional, and both the sending plan and the receiving plan have to participate before a match can move money.

Thirty-one thousand matched IRAs is progress. It is not the 31.9 million leftover 401(k)s, most of which never enter a default IRA because they sit above $7,000 or stay in the old plan. The network also cannot see a safe harbor IRA whose recordkeeper never joined, or a cash IRA a worker opened on purpose and then ignored. Until an IRA default other than cash is legal, the first stop for a forced small balance remains a product built to stand still.

How to Find a Left-Behind 401(k)

Start with the Labor Department’s lost-and-found if the money may still be in a private-sector 401(k) or pension, then check the old employer, state unclaimed property, and the Pension Benefit Guaranty Corporation if the company died. The federal site will not list an IRA, so a forced safe harbor account has to be chased through the IRA provider the old plan used, or through auto portability if both employers are in the network.

WHERE TO LOOK

• Former employer: HR or the plan administrator can still confirm a balance, a provider name, and whether the account was cashed out or rolled to a default IRA.
• Lost and Found: Search lostandfound.dol.gov after Login.gov identity checks; then call the administrator the site returns, because a listed plan does not prove money is still owed.
• Form 5500: The Labor Department’s EFAST2 filings name the current administrator when a company was sold or renamed.
• State unclaimed property: Checks under $1,000 and escheated IRA funds often land here; search the state where you lived and the state where the employer was based.
• PBGC: Use the Pension Benefit Guaranty Corporation search if a defined-benefit plan ended.

Once the account is found, a trustee-to-trustee transfer into a current 401(k) or a self-directed IRA moves the money without a check hitting your hands. If the leftover 401(k) is already in a low-fee target-date fund, leaving it there can be the boring choice that still compounds. If it has already been stuffed into a cash IRA, that is the balance that matches the dormant-fund warning, and it will not invest itself.

Reed’s line on inertia is the whole mechanism in one sentence: if you do nothing, cash stays cash. The safe harbor made that the official path for small leftover 401(k)s. The lost-and-found then went live without the authority to show the IRA those rules create. Until the default changes, a forced cash IRA earns whatever a principal-preservation product pays, and it keeps paying that until someone logs in and moves it.

Disclaimer: This article is news reporting and analysis of retirement-account rules and published data, and it is for information only. It is not investment, tax, or legal advice, and it is not a recommendation to buy, sell, roll over, or hold any IRA, 401(k), money market fund, or other product. Readers should consult a licensed financial advisor, tax professional, or the administrator of their own plan before moving retirement money, because rollovers, cash-outs, and asset mixes have tax and penalty consequences that depend on personal facts. Account counts, asset totals, yields, and the status of search tools and auto-portability networks reflect the cited sources on the dates given and can change.