On a paper federal return, you sign your tax return at the bottom of page 2 of Form 1040 in the block labeled “Sign Here,” directly under the refund and payment lines.1Internal Revenue Service. 2025 Form 1040 If you e-file, a five-digit Self-Select PIN takes the place of your handwritten signature, and if a paid preparer files for you, you sign Form 8879 to authorize them to transmit the return.2Internal Revenue Service. Self-Select PIN Method for Forms 1040 and 4868 Modernized e-File (MeF) Either way, the signature is a declaration under penalty of perjury that the return is accurate, and an unsigned return is not a valid return.
The Signature Block on Form 1040
Work your way through income, deductions, credits, and payments first. The signature area is the last thing you fill in on page 2. In the box next to “Your signature,” sign your name, then complete the date, your occupation, and your daytime phone number and email address on the same line. If you’re filing jointly, your spouse signs and dates the line directly below yours and fills in their own occupation.
Form 1040-SR, the version for taxpayers age 65 and older, uses larger type and wider spacing, which pushes the signature block to page 3 instead of page 2.3IRS.gov. 2025 Form 1040-SR U.S. Income Tax Return for Seniors The fields are otherwise the same.
The Identity Protection PIN Box
Next to the signature line is a small field labeled “If the IRS sent you an Identity Protection PIN, enter it here.”1Internal Revenue Service. 2025 Form 1040 The IP PIN is a six-digit number the IRS assigns to help stop someone from filing a fraudulent return under your Social Security number. It is not the same as the five-digit Self-Select PIN used when you e-file.
If you’ve been issued an IP PIN, you must enter it every time you file a federal return, including amended and prior-year returns.4Internal Revenue Service. IRS Online Account and Identity Protection PINs Protect Against Fraudsters If you don’t have one, leave the box blank.
The Paid Preparer Block
Below the taxpayer signature area is a separate section labeled “Paid Preparer Use Only.” If you prepared your own return, leave it blank. It exists only for someone paid to prepare the return, who must sign, date, and enter their Preparer Tax Identification Number (PTIN).1Internal Revenue Service. 2025 Form 1040 Missing any of those carries a preparer penalty of at least $60 per return, adjusted annually for inflation.5Internal Revenue Service. Tax Preparer Penalties
How to Sign an E-Filed Return
When you e-file yourself, you don’t sign anything by hand. You pick any five digits (except all zeros) as your Self-Select PIN, and the IRS verifies your identity by matching your date of birth and prior-year adjusted gross income against its records.2Internal Revenue Service. Self-Select PIN Method for Forms 1040 and 4868 Modernized e-File (MeF) If the AGI you enter doesn’t match, the return is rejected. You can pull last year’s AGI from the IRS’s Get Transcript tool if you don’t have a copy of the return.
First-time filers, or anyone who didn’t need to file last year, should enter zero for the prior-year AGI. Leaving the field blank causes a rejection. The prior-year PIN field should be left blank in that case.2Internal Revenue Service. Self-Select PIN Method for Forms 1040 and 4868 Modernized e-File (MeF)
When a Preparer E-Files for You
If a tax professional prepares and transmits your return, they use the Practitioner PIN method, and you sign Form 8879, the IRS e-file Signature Authorization. The form confirms you reviewed the return and authorize the preparer to send it.6Internal Revenue Service. Form 8879 (Rev. January 2021) – IRS e-file Signature Authorization You can return the signed form by mail, hand delivery, fax, or email. The preparer cannot transmit the return until they have your signed 8879.
Form 8879 carries the same legal weight as a pen-and-paper signature. Its perjury declaration is identical in substance to the one on paper Form 1040.7Office of the Law Revision Counsel. 26 USC 6061 – Signing of Returns and Other Documents
Signing a Joint Return
Both spouses must sign a married-filing-jointly return, even if only one spouse had income during the year.8Internal Revenue Service. Return Signature By signing, both of you accept joint and several liability for the entire tax owed, meaning the IRS can collect the full amount from either spouse regardless of who earned the income.
If your spouse cannot physically sign because of injury or illness but gives verbal permission, you can sign for them. Write your spouse’s name, then add “By [your name], Husband” or “By [your name], Wife,” and attach a dated statement explaining the situation.8Internal Revenue Service. Return Signature If you hold a formal power of attorney, attach a copy to the paper return or to Form 8453 for an e-filed return. Without either the written authorization or a signed statement, a joint return missing one spouse’s signature is invalid.
Signing for a Child
If your child has enough income to require a return but is too young to sign, you sign for them. Write the child’s name on the signature line, then add “By [your signature], parent for minor child.”9Internal Revenue Service. Publication 501 (2025), Dependents, Standard Deduction, and Filing Information A guardian or other legally responsible person signs the same way if no parent is available. This signature goes on the child’s own Form 1040, not on yours.
Signing for a Deceased Taxpayer
A final return must be filed for anyone who died during the year and had enough income to require one. Who signs depends on the relationship to the person who died.
- A surviving spouse filing jointly signs the return normally and writes “Filing as surviving spouse” next to the deceased spouse’s name in the signature area. Form 1310 is not required in this situation.10Internal Revenue Service. Form 1310 Statement of Person Claiming Refund Due a Deceased Taxpayer
- A court-appointed personal representative signs the return and attaches a copy of the court certificate showing the appointment. Form 1310 is not needed for the original return but is required if you later file an amended return or Form 843 claiming a refund.11Internal Revenue Service. Publication 559, Survivors, Executors, and Administrators
- If there is no surviving spouse and no court-appointed representative, whoever is in charge of the deceased person’s property signs as “personal representative” and must attach Form 1310.10Internal Revenue Service. Form 1310 Statement of Person Claiming Refund Due a Deceased Taxpayer
A power of attorney or a copy of the deceased person’s will is not sufficient proof of appointment. The IRS requires the actual court certificate.11Internal Revenue Service. Publication 559, Survivors, Executors, and Administrators
What Happens If You Forget to Sign
An unsigned return is not a valid return. The IRS will not process it and will not issue a refund.12Internal Revenue Service. Signing Form 1040 For paper filings, the IRS typically mails the return back and asks you to sign and resubmit. Missing the date or occupation fields can also cause delays.
The bigger risk is behind the scenes. The IRS generally has three years from the date you file a valid return to audit you. An unsigned return never starts that clock, so the IRS could assess additional tax at any point in the future.13Internal Revenue Service. 25.6.1 Statute of Limitations Processes and Procedures A delayed refund is annoying; an indefinitely open audit window is a real problem. If you realize after mailing that you forgot to sign, contact the IRS or your tax professional right away rather than waiting for the return to come back.