How the IRS Applies Your Payments: Tax, Then Penalty, Then Interest

If you owe for more than one year, every payment raises a question: which year, and which part of that year? Tax, penalty, or interest? The IRS has default answers. You can override them, but only if you say so at the right time, in writing. Most people never do.

Voluntary payments: you can designate

IRM 5.1.2.9 defines a designated payment as a voluntary payment the taxpayer has directed to be applied in a particular manner: to a specific period, to a kind of tax, or to tax or interest specifically. It says such a direction will normally be followed.

A voluntary payment is one you choose to make: a check, an online payment, an installment payment you send. The designation should go with the payment, in writing. A cover letter or the memo line plus the payment voucher for the specific year works. A designation after the fact is a request, not a right.

Undesignated and involuntary payments: the IRS chooses

IRM 5.1.2.9 says undesignated voluntary payments are applied consistent with Rev. Proc. 2002-26. IRM 5.1.2.6.4.1 describes the result: credits from involuntary payments or undesignated voluntary payments are applied in the order that best serves the interests of the government, considering the collection statute expiration date for each liability, which generally means oldest tax, then oldest penalty, then oldest interest, until used up.

Involuntary payments, like levy proceeds or a refund offset, cannot be designated at all. The IRS applies them.

Within a single year: tax first

For computing penalties, IRM 20.1.2.3.8.2 applies payments within a module to tax first, then to assessed penalties other than the failure-to-pay penalty, then to the failure-to-pay penalty, and finally to interest. Paying tax first shrinks the base for the failure-to-pay penalty and for interest, so within one year the default is usually in your favor. See the failure-to-pay guide.

Worked example: two years, one $8,000 check

Assume the following balances on October 15, 2026. The 2019 assessment's collection statute expires March 2027. The 2023 year has years left.

Option 1: undesignated

In five months the 2019 balance would have expired on its own. Of the $8,000 paid, $7,700 went to a debt the IRS was about to lose the right to collect. Meanwhile, all $12,000 of 2023 tax keeps drawing interest and failure-to-pay penalty.

Option 2: designated to 2023 tax

Now price the difference on the 2023 year for one year of time, at the 7 percent rate in Rev. Rul. 2026-15 and the 0.5 percent monthly failure-to-pay rate:

And if 2019 expires as scheduled, the $7,700 that Option 1 spent there was money the taxpayer never needed to pay. Same check. Very different result.

When to designate, and to what

• Years close to the CSED. Usually the last place you want voluntary money to go. See how the CSED is calculated.
• Years that may be dischargeable in bankruptcy. Paying a dischargeable year instead of a nondischargeable one can be backwards. See Can Chapter 7 Discharge Tax Debt?.
• Trust fund taxes. A business paying payroll taxes can designate to the trust fund portion, which reduces the personal exposure of responsible persons. See designating payroll payments.
• Tax versus interest in one year. Paying tax first stops the failure-to-pay penalty base from growing. The penalty and interest computations in IRM 20.1.2.3.8.2 already favor tax first.

Limits on designation

• Levies and offsets are involuntary. No designation.
• Expired years. IRM 5.1.2.6.4.1 says the IRS will not apply a payment to an assessment whose CSED has expired unless the taxpayer gives permission or the IRM allows it, for example certain levy proceeds from a levy served before the CSED.
• Collection's own rule. IRM 5.1.19.4 tells collection employees to apply payments to the module with the most imminent CSED first, and says that includes levy and seizure proceeds, installment agreement payments, and other undesignated voluntary payments. It also notes that a later tax period can have a more imminent CSED than an earlier one.

How to designate

1. Pay by a method that identifies the tax form and year. For online payments, choose the specific year carefully.
2. For mailed payments, include a short signed letter: name, taxpayer identification number, form, tax year, and what to apply it to (for example, tax for 2023).
3. Keep proof. If the transcript shows the payment posted elsewhere, ask the IRS to correct it, with your letter attached.

Check the result on your account transcript after posting. Payment transaction codes (such as TC 670 for a subsequent payment) show which module received the money.

What Rev. Proc. 2002-26 actually says

Rev. Proc. 2002-26, 2002-15 I.R.B. 746, is short and worth reading in the original. Section 3.01 says that when tax, penalty, and interest have been assessed (or agreed but unassessed) and the taxpayer voluntarily tenders a partial payment that the IRS accepts, with specific written directions, the IRS will apply the payment according to those directions.

Section 3.02 covers the undesignated case. The IRS applies the payment to periods in the order of priority it determines will serve its best interest, satisfying successive periods in descending order of priority until the payment is absorbed. Within a period, if the amount applied is less than the liability, it goes to tax, then penalty, then interest, in that order. Section 3.03 applies similar best-interest rules to payments under an accepted offer in compromise unless the offer and any collateral agreement provide otherwise. The revenue procedure superseded three older revenue rulings on the subject, and current IRM sections, including IRM 5.1.2.9 and IRM 5.7.4.3 (revised 2025), still apply it.

Note what the revenue procedure does not say: it does not use the phrase oldest year first. That is how IRM 5.1.2.6.4.1 describes the usual result of the best-interest standard, and IRM 5.1.19.4 refines it by directing collection employees to the module with the most imminent CSED, which is usually, but not always, the oldest year.

Worked example: one year, tax versus penalty

Say a single year shows $2,000 of tax, $1,500 of penalties, and $900 of interest, and you send $3,000 with no instructions. Under section 3.02, the IRS applies $2,000 to tax and $1,000 to penalties, leaving $500 of penalty and $900 of interest. That default is usually good for you within a single year, because it stops the failure-to-pay penalty base and the interest base from growing.

For a business, section 3.04 adds a tax wrinkle: any part of a payment applied to interest under the revenue procedure is treated as interest paid for purposes of IRC 163 in the year applied. Whether that interest is deductible depends on the taxpayer; for most individuals, interest on federal income tax is nondeductible personal interest.

Worked example: a designation that backfires

Designation is a tool, not a reflex. Suppose a taxpayer designates a $5,000 payment to the newest year because it has the longest CSED, but the older year is the one that is nondischargeable in a planned bankruptcy and the newer year will be discharged. The designation sent money to a debt that was about to disappear anyway. The right designation depends on the full map: CSEDs, dischargeability, trust fund exposure, and which year is accruing the most penalty and interest.

The bottom line

The IRS applies undesignated money to the oldest tax, penalty, and interest first, because that is what protects the government. Your best use of the same dollar may be the opposite. Designate voluntary payments in writing, every time. If you owe for several years, have someone map the CSEDs before you write the next check.