How IRS Overpayment Interest on Refunds Is Calculated

Most of this site is about what the IRS charges you. This page is about what the IRS pays you. The rules are just as mechanical, and the IRS applies them without being asked. If you are owed interest, you should know how to check it.

The rate

IRC 6611(a) pays interest on an overpayment at the overpayment rate under IRC 6621(a)(1): the federal short-term rate plus 3 percentage points for individuals. For corporations it is plus 2, and only plus 0.5 on the portion of a corporate overpayment above $10,000.

Like underpayment interest, overpayment interest compounds daily under IRC 6622. The full rate table is in IRS interest rates by quarter.

When the clock starts: the date of the overpayment

Interest runs from the date of the overpayment. For withholding and estimated tax payments, IRC 6611(d) borrows the rules of IRC 6513: those payments are treated as made on the due date of the return, without extensions. So for a 2025 individual return, withholding and estimates are deemed paid April 15, 2026, and an overpayment from them dates from April 15, 2026.

When the clock ends

• Refund: IRC 6611(b)(2) runs interest to a date the IRS chooses, not more than 30 days before the date of the refund check.
• Credit against another balance: IRC 6611(b)(1) runs interest only to the due date of the amount the credit is applied against. If you apply this year's overpayment to next year's estimated tax, both dates are the same April 15, so there is no interest at all.

The four rules that cut interest off

1. The 45-day rule for original returns. IRC 6611(e)(1): no interest if the refund is paid within 45 days after the return due date (without extensions), or, for a return filed after that date, within 45 days after it is filed.
2. Late returns. IRC 6611(b)(3): if the return is filed after its due date (with extensions), no interest for any day before the return is filed.
3. Claims for refund. IRC 6611(e)(2): if a refund claim is paid within 45 days of filing the claim, no interest from the claim date to the refund date.
4. IRS-initiated adjustments. IRC 6611(e)(3): when the IRS initiates the adjustment, interest is reduced by 45 days.

One more: IRC 6611(g) says a return is not filed for these purposes until it is in processible form, meaning on a permitted form, signed, with enough information to verify the tax. An incomplete return does not start the 45 days.

Example A: early filer, fast refund

You file your 2025 return March 1, 2026 and the refund is issued April 20, 2026. That is within 45 days after the April 15 due date. Interest: zero. This is how most refunds work, and why most people never see refund interest.

Example B: extension filer

You file your 2025 return on extension, September 1, 2026, claiming a $3,000 refund of withholding. The refund is issued November 20, 2026. The return was timely (extended), so 6611(b)(3) does not apply. The refund came more than 45 days after April 15, so 6611(e)(1) does not block interest either.

Example C: late return, no extension

Same $3,000 refund, but no extension and the return is filed August 1, 2026. Under 6611(b)(3), no interest for any day before August 1. Under 6611(e)(1), no interest at all if the refund is paid within 45 days after filing, which is by September 15, 2026.

Example D: amended return claim

In June 2026 you discover your 2024 return overstated income. You file Form 1040-X on June 1, 2026, claiming a $5,000 refund. The overpayment dates from April 15, 2025. The IRS pays on July 1, 2026, within 45 days of the claim.

The 45-day rule on claims only blocks interest after the claim is filed. Everything before that is still owed.

Offsets and credits

If you owe another balance, the IRS can credit your overpayment against it under IRC 6402 instead of refunding it. Interest on the overpayment then runs only to the due date of the balance it is applied against, under 6611(b)(1). If that balance's due date is earlier than the overpayment date, there is no overpayment interest. And IRC 6601(f) says the tax satisfied by the credit stops drawing underpayment interest for the period the overpayment would have earned interest. The two sides cancel.

For corporations with overlapping underpayments and overpayments at different rates, IRC 6621(d) goes further and nets the rates to zero. See interest netting.

Interest you receive is income

Overpayment interest is taxable interest income in the year you receive it, and the IRS reports it to you. Do not forget it on next year's return. A $401.87 interest payment you ignore can become its own small underreporter notice.

Checking the IRS figure

1. Identify the overpayment date (usually the original due date for withholding and estimates, or the actual payment date for later payments).
2. Identify the later of the return filing date (if late) or the overpayment date as the start.
3. Apply the 45-day rules for original returns, claims, and IRS-initiated adjustments.
4. Compound daily at the quarterly overpayment rates to the IRS cutoff date, up to 30 days before the check.

For how the IRS applies payments and credits across years, see how the IRS applies payments. For daily compounding, see how IRS interest compounds daily.

Worked example: a corporate refund

Corporations earn less and the rate splits at $10,000. Under IRC 6621(a)(1), a corporate overpayment earns the federal short-term rate plus 2 percentage points, but only plus 0.5 on the portion above $10,000. For the fourth quarter of 2026, Rev. Rul. 2026-15 sets those at 6 percent and 4.5 percent.

Say a corporation has a $50,000 overpayment earning interest for all 92 days of the fourth quarter of 2026. The first $10,000 earns 6 percent compounded daily, and the remaining $40,000 earns 4.5 percent. Total interest for the quarter is $608.62. An individual with the same $50,000 overpayment would earn 7 percent on all of it, or $889.93 for the same 92 days. The corporate split costs about $281 in a single quarter.

That gap is why corporations with offsetting balances look hard at interest netting under IRC 6621(d), which can equalize the rates during overlapping periods. Rev. Proc. 2000-26 describes how to request it on Form 843.

Worked example: a credit elect

Many taxpayers apply an overpayment to next year's estimated tax instead of taking a refund. Under IRC 6611(b)(1), interest on a credit runs from the date of the overpayment to the due date of the amount against which the credit is taken. For a 2025 overpayment from withholding, the overpayment date is April 15, 2026 under IRC 6513 and 6611(d), and the first 2026 estimated payment is also due April 15, 2026. Same start and end date, so no interest. That is not a penalty; it is the arithmetic of a credit applied on the day it arises.

Offsets work the same way. If the IRS applies a 2025 overpayment to an older balance due, IRC 6611(b)(1) ends overpayment interest at the due date of the balance it is applied against, and IRC 6601(f) stops underpayment interest on the satisfied tax for the period the overpayment would have earned interest. The account nets out without anyone paying a spread.

The bottom line

The IRS pays interest on refunds at the overpayment rate, from the overpayment date, compounded daily, but only after clearing the 45-day rules and only from the filing date on late returns. File on time and the timing rules favor you. If an amended claim or an audit refund looks light on interest, the formula above will tell you whether to ask.