On a paper Form 1040, you sign in ink in the box marked “Sign Here” at the bottom of page 2. When you e-file, there is no paper to sign, so where to sign your tax return becomes a question of identity verification instead: you enter a five-digit Self-Select PIN and confirm it with your prior-year adjusted gross income or your Identity Protection PIN. Either method counts as your legal signature, and federal law treats the two the same.1Office of the Law Revision Counsel. 26 U.S. Code 6061 – Signing of Returns and Other Documents
Signing a Paper Form 1040
Flip to page 2. Near the bottom you’ll find a block labeled “Sign Here” with a line for your signature, the date, and your occupation. Right next to that is a small box for an Identity Protection PIN if the IRS has issued you one.2Internal Revenue Service. Form 1040 (2024)
Sign with a pen. The IRS won’t accept a photocopied, stamped, or typed signature on a paper return. If a paid preparer completed your return, they sign the separate “Paid Preparer Use Only” section directly below your signature area and enter their Preparer Tax Identification Number. Your signature obligation is unchanged by theirs; you are still the one making the declaration.
State returns work the same way in concept. The signature line sits near the end of the form, and the exact page depends on the state.
Signing an E-Filed Return
Electronic filing replaces the pen with a PIN. Your tax software walks you through it, but the pieces are worth understanding so you know what’s being asked and why a return sometimes gets rejected at this step.
Self-Select PIN
You choose any five-digit number other than all zeros. That number is your signature.3Internal Revenue Service. Self-Select PIN Method for Forms 1040 and 4868 Modernized e-File (MeF) To prove the PIN belongs to you, the system also asks for your date of birth and either your prior-year AGI or the Self-Select PIN you used last year.
If you don’t remember your prior-year AGI, you can look it up in your IRS online account under the Tax Records tab, or request a transcript by mail. First-time filers enter zero. If last year’s return is still being processed by the IRS, enter zero for that too.4Internal Revenue Service. Validating Your Electronically Filed Tax Return AGI mismatches are one of the more common causes of e-file rejection, and trying zero often solves it.
Identity Protection PIN
If the IRS has issued you an IP PIN, you must enter it when you e-file. It’s a six-digit number that replaces the AGI check. Enter it wrong and the return is rejected.5Internal Revenue Service. FAQs About the Identity Protection Personal Identification Number (IP PIN) On paper returns, the IP PIN goes in the dedicated box next to your signature.
Practitioner PIN and Form 8879
When a preparer e-files for you, they typically use a Practitioner PIN, but only after you authorize the filing by signing Form 8879, the IRS e-file Signature Authorization.6Internal Revenue Service. About Form 8879, IRS e-file Signature Authorization You can sign Form 8879 with a pen or with an electronic signature if the preparer’s software supports it.7Internal Revenue Service. Form 8879 (Rev. January 2021) That form is your authorization for the preparer to transmit the return on your behalf.
Joint Returns
Both spouses must sign a joint return. On paper, page 2 of Form 1040 has separate signature lines for each spouse, and both must sign and date. When e-filing, each spouse enters their own Self-Select PIN.8Internal Revenue Service. Topic No. 255, Signing Your Return Electronically If a preparer is filing, both spouses sign Form 8879.9Internal Revenue Service. Quality Review of the Tax Return – Signing Form 1040
One spouse can’t simply sign for the other. If a spouse is deployed, ill, or otherwise unavailable, the return either waits for their signature or requires a valid power of attorney that specifically authorizes tax return signing.
Signing on Behalf of Someone Else
Sometimes the person who owes the return can’t sign it themselves. The rules turn on the reason.
A minor child. A parent or guardian signs the child’s return by writing the child’s name on the signature line, followed by “by,” then the parent’s signature and the relationship, such as “parent” or “guardian for minor child.”10Internal Revenue Service. Topic No. 301, When, How and Where to File
A deceased taxpayer. A surviving spouse filing jointly signs the return and writes “filing as surviving spouse” in the deceased person’s signature area. If there is a court-appointed representative, that person also signs. Where there is no surviving spouse, the court-appointed representative signs and attaches the appointment document. If there is neither, whoever is in charge of the deceased person’s property signs as “personal representative.” On a paper return, write “deceased,” the person’s name, and the date of death across the top. Claiming a refund due to a deceased taxpayer generally requires Form 1310, unless you’re the surviving spouse or a court-appointed representative.11Internal Revenue Service. Filing a Final Federal Tax Return for Someone Who Has Died
An incapacitated taxpayer. The IRS allows an agent to sign only in narrow circumstances: the taxpayer has a disease or injury that prevents them from signing, has been continuously outside the United States for at least 60 days before the filing deadline, or has been granted specific permission by the IRS for other good cause. The agent files Form 2848 (Power of Attorney and Declaration of Representative) with the “Sign a return” box checked and the qualifying reason identified. A general power of attorney that doesn’t specifically address tax return signing isn’t enough. On paper, attach Form 2848 to the return; if e-filing, attach it to Form 8453 and mail that in separately.12Internal Revenue Service. Instructions for Form 2848 (Rev. September 2021)
Why the Signature Matters
The line above the signature block on Form 1040 reads: “Under penalties of perjury, I declare that I have examined this return and accompanying schedules and statements, and to the best of my knowledge and belief, they are true, correct, and complete.” Federal law requires that declaration on every return.13Office of the Law Revision Counsel. 26 U.S. Code 6065 – Verification of Returns Whether you signed with a pen or a PIN, you personally vouch for what’s on the return, and knowingly false entries can lead to fraud or evasion charges beyond an ordinary audit.
What Happens If the Return Isn’t Signed
An unsigned return isn’t a valid return. The IRS won’t process it and won’t release any refund; instead, the return comes back to you to sign and resubmit.9Internal Revenue Service. Quality Review of the Tax Return – Signing Form 1040 If you filed on time and paid what you owed, the IRS generally won’t hit you with a late-filing penalty on the initial unsigned return so long as you sign and return it when asked.14Internal Revenue Service. Policy Statement P-3-5
The quieter risk is the statute of limitations. The three-year window the IRS has to audit a return runs from the date it was filed, and an unsigned return doesn’t count as filed. Until you sign, that clock never starts.
On the electronic side, a mismatched PIN, wrong prior-year AGI, or incorrect IP PIN causes an immediate rejection. Your software tells you what failed, and you can correct and resubmit. As long as the corrected return arrives by the filing deadline, there’s no penalty.