How to Write a Check to the IRS: Payee, Memo Line, and Voucher

To write a check to the IRS, make it payable to “United States Treasury,” write the dollar amount in both figures and words, and put your Social Security number, the tax year, and the form number on the memo line. Sign it, add your daytime phone number, and mail it loose (no staples) with the matching payment voucher to the address the IRS lists for your state. The details below are what keeps the payment from sitting in limbo.

What Goes on Each Line of the Check

The Payee

The Form 1040-V instructions say to make the check payable to “United States Treasury.”¹ The IRS’s general payment page also accepts “U.S. Treasury.”² Do not write “IRS” alone as the payee. Banks may refuse to process a check made out that way.

The Amount

Enter the numerical amount in standard decimal format, like $1,250.00. The IRS specifically says not to use dashes or fraction notation such as “$1,250—” or “$1,250 xx/100.”¹ Spell the same figure out on the written-amount line. If the two disagree, the bank goes by the words, so a transposed digit in one place can cause the wrong amount to clear.

The Memo Line

This is the field that causes the most trouble when it’s left blank. Write all three of these on or near the memo line:

Your Social Security number, EIN, or ITIN
The tax year (for example, 2025)
The form number, or the notice number if you’re paying in response to a notice (for example, “Form 1040” or “CP14”)

A complete memo line reads something like “123-45-6789, 2025 Form 1040.” Joint filers should use the SSN listed first on the return. If you and your spouse filed jointly but got separate balance-due notices, also add “MFT 31 separate assessment” so the IRS credits the right portion to the right spouse.²

Your Phone Number and Signature

Write a daytime phone number somewhere on the face of the check so the IRS can reach you with any question about the payment.² Then sign it. An unsigned check goes nowhere.

The Voucher That Goes With It

A check by itself is rarely enough. The IRS uses a payment voucher to route your money to the right account before anyone reads the memo line.

If you owe a balance on Form 1040, 1040-SR, or 1040-NR, include Form 1040-V.³ You fill in your name, address, SSN, and the amount you’re paying. It takes about a minute.

If you’re paying quarterly estimated taxes, use a Form 1040-ES voucher instead. The form comes with four tear-off vouchers, one per quarterly due date.⁴

If you’re mailing a check with an extension request, include Form 4868. An extension gives you more time to file, not more time to pay. Interest and penalties still run on any unpaid balance from the original due date.

Packaging the Envelope

Do not staple or paperclip the check to the voucher or to the return. Put everything in loose.¹ The IRS runs envelopes through automated equipment, and staples jam the machines. Place the check on top of the voucher, and the voucher on top of the return if you’re including one.

Never send cash in the mail.

Where to Mail It

There is no universal IRS address. The correct one depends on which form you’re filing and which state you live in. The IRS publishes the list on its website, organized by state and by form, with different addresses for returns with a payment versus returns without.⁵ The Form 1040-V instructions also print the applicable addresses on the back.

Sending your payment to the wrong service center won’t void it, but it can add weeks while the IRS reroutes the envelope internally.

Private Delivery Services

If you use FedEx, UPS, or DHL, only certain service levels are IRS-designated for timely-mailing purposes. Approved options include FedEx Priority Overnight, UPS Next Day Air, and DHL Express, among others.⁶ Standard ground shipping from those carriers does not qualify. If you use a non-designated service and the payment arrives late, the IRS treats it as late no matter when you handed it over.

Proving You Mailed It on Time

Under the federal mailbox rule, a tax payment postmarked on or before the due date counts as paid on time, even if the IRS receives it days later.⁷ The postmark is the whole ballgame. A regular USPS postmark now reflects when the item was first processed at a regional facility, which can be a day or two after you dropped it in a mailbox.

Three ways to lock in the date you actually handed the mail over:

Buy postage at the counter. The printed label shows the acceptance date.
Ask for a hand-stamped postmark at the window.
Buy a Certificate of Mailing. The receipt proves the date USPS took possession.

Certified Mail is stronger still, because it gives you proof of both mailing and delivery, which matters if the IRS later claims it never received the payment.⁸ Self-service kiosk labels and Click-N-Ship labels only prove you bought postage, not that USPS accepted the item on that date. Close to a deadline, Certified Mail with a return receipt is cheap insurance.

If the Check Bounces

A dishonored check triggers a separate penalty on top of whatever you already owe.⁹ For checks of $1,250 or more, the penalty is 2% of the check amount. For checks under $1,250, the penalty is the amount of the check or $25, whichever is less. And because the underlying tax is still unpaid, the failure-to-pay penalty and interest keep running until you make good on the balance.

If You Can’t Pay the Full Amount

File on time anyway and send whatever you can. The IRS is explicit that the failure-to-file penalty is far steeper than the failure-to-pay penalty.¹⁰ Every dollar you send reduces the base on which penalties and interest accrue.

The failure-to-pay penalty is 0.5% of the unpaid balance per month or partial month, capped at 25%.¹¹ It drops to 0.25% per month if you filed on time and have an approved payment plan. Interest runs separately on top of that.

Two payment plans are available for the remaining balance: a short-term plan of 180 days or less, and a long-term installment agreement with monthly payments. Both can be applied for online at IRS.gov, which is faster and cheaper than applying by phone or mail.¹²

One Alternative Worth Considering

Mailing a check is legitimate, but IRS Direct Pay lets you pay from a bank account for free and gives you immediate confirmation the payment was received.¹³ An electronic payment made before midnight on the due date is on time with no postmark question. If you’re pushing up against a deadline, it removes the parts of the mailed-check process most likely to go wrong.

1
Internal Revenue Service. Form 1040-V (2025) Payment Voucher for Individuals
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Internal Revenue Service. Pay by Check or Money Order
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Internal Revenue Service. About Form 1040-V, Payment Voucher for Individuals
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Internal Revenue Service. About Form 1040-ES, Estimated Tax for Individuals
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Internal Revenue Service. Where to File Paper Tax Returns With or Without a Payment
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Internal Revenue Service. Private Delivery Services (PDS)
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GovInfo. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying
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FAQ | USPS. Mailing Your Tax Return
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Internal Revenue Service. Dishonored Check or Other Form of Payment Penalty
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Internal Revenue Service. Topic No. 202, Tax Payment Options
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Internal Revenue Service. Failure to Pay Penalty
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Internal Revenue Service. Payment Plans; Installment Agreements
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Internal Revenue Service. Pay Personal Taxes From Your Bank Account