How Does a 401(k) Loan Work?

Key Takeaways

• A 401(k) loan lets you borrow from your own retirement balance and pay yourself back with interest, with no taxes or penalties as long as you repay on schedule.
• The IRS caps the loan at the lesser of $50,000 or 50% of your vested balance.
• Most loans must be repaid within five years through payroll deductions, though a loan to buy your primary home can run longer.
• Leaving your job can make the balance due quickly, and an unpaid loan becomes a taxable distribution plus a 10% penalty if you are under 59 and a half.

What a 401(k) loan is

A 401(k) loan lets you borrow money from your own workplace retirement account and repay it, with interest, back to yourself. Because it is structured as a loan rather than a withdrawal, it is not treated as a taxable distribution, so you avoid both the income tax and the early-withdrawal penalty that would normally apply before age 59 and a half.

Employers are not required to offer loans, so the first step is confirming your plan allows them and reading its specific rules. If it does, the money comes out of your account balance, and your repayments (principal plus interest) flow back into the account over time. You can model a payment and payoff on your own balance with the 401(k) Loan Calculator before you commit.

The appeal is obvious: no credit check, a low rate, and interest that lands in your own account instead of a bank's. But a 401(k) loan borrows against your future, and the rules around repayment and job changes are where the real risk lives.

How much you can borrow

Federal law limits a 401(k) loan to the lesser of $50,000 or 50% of your vested account balance, a ceiling set by the IRS^[1]. If your vested balance is $80,000, your ceiling is $40,000. If it is $300,000, the $50,000 cap applies rather than the full half. Some plans allow a minimum of up to $10,000 even when that exceeds half the balance, but not every plan does.

The loan is funded by selling investments inside your account, and the interest rate is set by your plan, commonly the prime rate plus one percentage point. That rate is usually well below a credit card or an unsecured personal loan, and because you pay the interest to yourself, it does not leave your household the way interest to a lender does.

You can only borrow from your current employer's plan. Balances at former employers are off limits unless you first roll them into your current plan, and Individual Retirement Accounts cannot offer loans at all.

How repayment works

Repayment terms are set by the IRS and your plan administrator. In most cases you must repay within five years, with payments made at least quarterly on a substantially level schedule, as the IRS requires^[2]. In practice, repayment almost always happens automatically through payroll deductions, which makes a 401(k) loan very hard to fall behind on while you remain employed.

There is one important exception to the five-year rule: a loan used to buy your primary residence can be repaid over a longer period, often up to 15 years, depending on the plan. That longer runway lowers the payment but stretches out the time your money is sitting outside the market.

Because the payments are automatic and the rate is low, the loan feels painless month to month. The costs that matter are the ones that do not show up on your paycheck, which the next two sections cover.

What happens if you leave your job

This is the trap most borrowers underestimate. If you leave your employer, by choice or not, with a loan outstanding, the unpaid balance is generally treated as a loan offset. You are not billed for it, but the outstanding amount is deducted from your account balance.

To avoid that offset being taxed as a distribution, you have until the due date of your federal tax return, including extensions, for the year the offset occurs to roll an equivalent amount into an IRA or a new employer's plan to avoid a taxable distribution^[3]. This deadline is far more generous than the 60 days that applied before 2018, but it is still a hard deadline.

Miss it and the offset becomes ordinary taxable income for that year, plus the 10% early-withdrawal penalty if you are under 59 and a half. A job change is exactly when cash is often tight, which is what makes this risk so easy to stumble into.

The real cost of borrowing from yourself

"Paying interest to yourself" sounds like a free lunch, but there are two hidden costs. The first is opportunity cost. The money you borrowed is no longer invested, so it misses whatever the market returns^[4] while the loan is outstanding. Over several years, that forgone growth can dwarf the interest you pay yourself, especially in a strong market.

The second is a subtle double taxation on the interest. You repay the loan with after-tax dollars, and then you pay tax again on those same dollars when you withdraw them in retirement. Neither cost appears on a statement, which is why a 401(k) loan almost always feels cheaper than it truly is.

There is also a contribution risk. Some people reduce or pause their regular 401(k) contributions while repaying a loan. If that means giving up an employer match, you are walking away from an immediate, guaranteed return that no loan rate can offset. You can see how missed growth compounds over time with the compound interest calculator.

When a 401(k) loan makes sense

A 401(k) loan can be reasonable for a short-term, high-priority need when the alternative is clearly worse. Consolidating high-rate credit card debt, covering a genuine emergency, or funding a home down payment large enough to eliminate private mortgage insurance are the cases most often cited. It works best when your job is stable and you can repay quickly.

It is a poor choice for discretionary spending, for anyone whose employment is uncertain, or when repaying it means giving up an employer match. Draining future retirement growth to fund a vacation or a lifestyle upgrade rarely pencils out once the hidden costs are counted.

Before borrowing, compare it honestly against the alternatives: a personal loan, a home equity option, or simply waiting and saving. A 401(k) loan is a tool, not a trap, but only when you go in with a clear repayment plan and a stable income behind it.

Frequently Asked Questions

Does a 401(k) loan affect my credit score?

No. There is no credit check to borrow, and the loan is not reported to the credit bureaus, so it neither helps nor hurts your credit score.

How much can I borrow from my 401(k)?

The IRS limit is the lesser of $50,000 or 50% of your vested account balance. Your plan may set a lower limit, so confirm the details with your administrator.

Can I borrow from an old employer's 401(k) or an IRA?

No. You can only borrow from your current employer's plan. IRAs cannot offer loans. Rolling an old 401(k) into your current plan can make those funds borrowable.

Is the interest on a 401(k) loan tax-deductible?

No. Unlike mortgage interest, 401(k) loan interest is never deductible, and it is paid with after-tax dollars that get taxed again when you withdraw them in retirement.

What happens if I cannot repay the loan?

The unpaid balance is treated as a deemed distribution: it becomes taxable income, plus a 10% early-withdrawal penalty if you are under 59 and a half.