On a paper Form 1040, you sign at the bottom of page 2 in the box labeled “Sign Here.” When you e-file, you don’t sign anything physical; instead, you enter a five-digit Self-Select PIN (or a six-digit Identity Protection PIN if the IRS has issued you one) after verifying your identity with your prior-year adjusted gross income or last year’s PIN. Either way, the signature is mandatory. An unsigned return is not a valid return, and the IRS will not process it or release any refund until you fix it.
Signing a Paper Form 1040
Flip to page 2 of Form 1040 and look at the bottom. You’ll see a block labeled “Sign Here” with a line for your signature, the date, your occupation, and a small box for an Identity Protection PIN if you have one.1Internal Revenue Service. Form 1040 (2024) Sign in ink. The IRS does not accept photocopied, stamped, or typed signatures on paper returns.
Just above that line is the perjury declaration: by signing, you are stating under penalty of perjury that the return is true, correct, and complete to the best of your knowledge.2Office of the Law Revision Counsel. 26 U.S. Code 6065 – Verification of Returns That carries weight whether a preparer built the return or you did it yourself at the kitchen table.
If you’re filing jointly, both spouses have their own signature lines in the same block, and both must sign and date.3Internal Revenue Service. Quality Review of the Tax Return – Signing Form 1040 One spouse cannot sign for the other except in narrow circumstances covered further down.
Signing an E-Filed Return
With e-file, your “signature” is an electronic PIN tied to an identity check. Federal law treats that electronic signature the same as a handwritten one, including for perjury purposes.4Office of the Law Revision Counsel. 26 U.S. Code 6061 – Signing of Returns and Other Documents There are three common methods, depending on who is filing.
Self-Select PIN
If you’re preparing your own return in tax software, you’ll be asked to choose any five-digit number (other than all zeros) as your electronic signature.5Internal Revenue Service. Self-Select PIN Method for Forms 1040 and 4868 Modernized e-File (MeF) To prove you’re really you, the system also asks for your date of birth plus either your prior-year AGI or the Self-Select PIN you used last year.
If you can’t find last year’s AGI, pull it from 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, enter zero as well.6Internal Revenue Service. Validating Your Electronically Filed Tax Return A rejected e-file with an AGI error code is almost always fixed by trying zero before anything else.
Identity Protection PIN
If the IRS has issued you an Identity Protection PIN (IP PIN), you must enter the current six-digit number when you e-file; it takes the place of the AGI check. Enter it wrong and the return is rejected.7Internal Revenue Service. FAQs About the Identity Protection Personal Identification Number (IP PIN) On a paper return, the IP PIN goes in the small box printed right next to the signature line.
Practitioner PIN
When a tax preparer e-files for you, they typically use a Practitioner PIN, but only after you authorize them in writing on Form 8879, the IRS e-file Signature Authorization.8Internal Revenue Service. About Form 8879, IRS e-file Signature Authorization You can sign Form 8879 by hand or electronically if the preparer’s software supports it.9Internal Revenue Service. Form 8879 (Rev. January 2021) Your preparer must hold onto that signed form for three years in case the IRS asks for proof you authorized the filing.10Internal Revenue Service. Form 8879 Record Retention Guidance
Joint Returns: Both Spouses Sign
A joint return is not valid unless both spouses sign.3Internal Revenue Service. Quality Review of the Tax Return – Signing Form 1040 On paper, that means two signatures on page 2. When e-filing, each spouse enters their own Self-Select PIN.11Internal Revenue Service. Topic No. 255, Signing Your Return Electronically If a preparer is submitting the return, both spouses sign Form 8879.
If your spouse is deployed, traveling, or otherwise unavailable, you can only sign for them if you hold a power of attorney that specifically authorizes signing a tax return. Without that, the absent spouse has to sign separately before the return goes in.
If You’re Using a Preparer
Hiring someone doesn’t shift the perjury declaration off your shoulders. Read the return, then sign it. On a paper 1040, your preparer signs the “Paid Preparer Use Only” section directly below your signature block and fills in their Preparer Tax Identification Number (PTIN), the firm’s name and address, and the firm’s EIN.1Internal Revenue Service. Form 1040 (2024) Every paid preparer must have a PTIN; a preparer who won’t provide one is a warning sign.
For an e-filed return handled by a preparer, your signature lives on Form 8879, not on the 1040 itself.
Signing for Someone Else
The IRS allows a signature on someone else’s behalf only in specific situations.
A Minor Child
If your child is too young to sign, write the child’s name on the signature line, add “by,” then sign your own name and note your relationship, such as “parent” or “guardian for minor child.”12Internal Revenue Service. Topic No. 301, When, How and Where to File
A Deceased Taxpayer
A final return still has to be filed, and who signs depends on the situation:
- Surviving spouse filing jointly: the surviving spouse signs the return and writes “filing as surviving spouse” in the deceased spouse’s signature area. A court-appointed representative, if there is one, also signs.13Internal Revenue Service. Filing a Final Federal Tax Return for Someone Who Has Died
- Court-appointed representative with no surviving spouse: the representative signs and attaches a copy of the court document showing the appointment.
- No representative and no surviving spouse: 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. If a refund is due, Form 1310 is required to claim it, unless you’re a surviving spouse or court-appointed representative.13Internal Revenue Service. Filing a Final Federal Tax Return for Someone Who Has Died
An Incapacitated Taxpayer
Signing another adult’s return takes more than a general power of attorney. The IRS requires Form 2848 (Power of Attorney and Declaration of Representative) with the “Sign a return” box checked, and the taxpayer must fall into one of three qualifying situations: a disease or injury preventing them from signing, continuous absence from the United States for at least 60 days before the filing deadline, or specific IRS permission for other good cause.14Internal Revenue Service. Instructions for Form 2848 (Rev. September 2021) Attach Form 2848 to a paper return. For an e-filed return, attach it to Form 8453 and mail that separately to the IRS.
What Happens If You Forget to Sign
An unsigned return is treated as never filed. The IRS mails it back and asks you to sign and resubmit, and no refund moves until that happens.3Internal Revenue Service. Quality Review of the Tax Return – Signing Form 1040 If you filed on time with proper payment, the IRS generally won’t hit you with a late-filing penalty for the original unsigned submission as long as you fix it promptly.15Internal Revenue Service. Policy Statement P-3-5
The quieter problem is the statute of limitations. The IRS normally has three years from the filing date to audit and assess additional tax. Because an unsigned return isn’t a filed return, that three-year clock never starts. In principle, the IRS could come back on that tax year with no time limit. A late-filing penalty can also apply if the IRS finds willful intent or gross negligence behind the missing signature.15Internal Revenue Service. Policy Statement P-3-5
With e-file, a missing or mismatched signature (wrong AGI, wrong IP PIN) triggers an immediate rejection from your software. Correct it and resubmit; as long as the fixed return arrives by the filing deadline, no penalty follows.