Form 8879-S is the IRS e-file signature authorization an S corporation officer signs so a tax preparer can transmit Form 1120-S electronically without a paper return. The officer’s five-digit PIN on the form stands in as the signature on the return itself, and if the corporation owes tax, the same form can authorize a direct debit from the corporation’s bank account.
What Signing Form 8879-S Does
The form creates a narrow grant of authority. By signing, a corporate officer confirms two things: that the figures on the electronically filed Form 1120-S are true and complete, and that the Electronic Return Originator (ERO) may transmit that return to the IRS using the PIN recorded on the form. The ERO cannot send the return until the signed authorization is in hand.1Internal Revenue Service. Form 8879-S – IRS e-file Signature Authorization for Form 1120-S
If the return shows a balance due and the corporation wants to pay electronically, signing also authorizes the U.S. Treasury’s financial agent to pull the payment from the account entered in the tax software. That payment can be canceled by calling the Treasury Financial Agent at 888-353-4537 at least two business days before the scheduled withdrawal date.1Internal Revenue Service. Form 8879-S – IRS e-file Signature Authorization for Form 1120-S
Who Can Sign for the Corporation
Only someone authorized to sign the corporation’s income tax return can sign Form 8879-S. Under federal law, that means the president, vice president, treasurer, assistant treasurer, chief accounting officer, or any other officer the corporation has authorized to act in that capacity. A fiduciary filing on behalf of the corporation under Section 6012(b)(3) can sign as well.2Office of the Law Revision Counsel. 26 USC 6062 – Signing of Corporation Returns
The declaration above the signature line is made under penalties of perjury. The officer attests to having examined a copy of the electronic return and, to the best of their knowledge, believes it to be true, correct, and complete.1Internal Revenue Service. Form 8879-S – IRS e-file Signature Authorization for Form 1120-S A PIN submitted through the IRS’s authorized electronic methods carries the same legal weight as a handwritten signature.3Office of the Law Revision Counsel. 26 USC 6061 – Signing of Returns and Other Documents
How the Form Gets Filled Out
The form has three parts, and the officer only signs one of them.
Part I: Return Information
The ERO completes Part I, transferring key figures from the finalized Form 1120-S so the officer can verify them at a glance. These include total tax, any overpayment or refund, and the balance due. If a line doesn’t apply, the ERO enters zero rather than leaving it blank. The corporation’s legal name, Employer Identification Number, and tax year must match the prepared return exactly, because the IRS validates those against its records before accepting the transmission.1Internal Revenue Service. Form 8879-S – IRS e-file Signature Authorization for Form 1120-S
Part II: The Officer’s PIN and Signature
The officer’s PIN is any five-digit number except all zeros. The officer can pick the number personally, or the ERO or tax software can generate it. Either way, the officer reviews the PIN shown on the form and confirms it by signing and dating Part II.4Internal Revenue Service. About Form 8879-S, IRS e-file Signature Authorization for Form 1120S
Part III: The ERO’s Information
In Part III, the ERO enters a six-digit Electronic Filing Identification Number (EFIN) followed by a self-selected five-digit PIN. That combined entry serves as the ERO’s own signature, certifying the submission complies with IRS Publications 3112 and 4163. The ERO signs, dates Part III, and transmits the return, with the officer’s PIN from Part II embedded in the electronic data as the return’s signature.1Internal Revenue Service. Form 8879-S – IRS e-file Signature Authorization for Form 1120-S
When to Sign
The officer must sign after Form 1120-S is finalized but before the ERO transmits it. A signature on a draft return is invalid, because the officer can’t truthfully attest to figures that haven’t been locked in. The date next to the signature should reflect the actual day the officer reviewed and approved the final return.1Internal Revenue Service. Form 8879-S – IRS e-file Signature Authorization for Form 1120-S
A paper signature is not required. The IRS allows e-signatures on 8879-series forms when the ERO’s software includes identity verification, captures a digital image of the signed form with a timestamp, and records the signer’s IP address, login ID, verification result, and signature method. If the officer fails knowledge-based authentication after three attempts, the ERO must collect a handwritten signature instead.5Internal Revenue Service. Frequently Asked Questions for IRS e-file Signature Authorization
If the Return Gets Rejected
The most common rejection for business returns is a mismatch between the EIN and the IRS-assigned four-character “name control” derived from the corporation’s legal name. Any discrepancy in the return header triggers an automatic rejection.6Internal Revenue Service. Using the Correct Name Control in E-filing Corporate Tax Returns
If the corporation recently changed its name and that caused the mismatch, the ERO should check the Name Change box on Form 1120-S and retransmit. For other name control issues, the ERO can call the IRS e-Help Desk at 1-866-255-0654.6Internal Revenue Service. Using the Correct Name Control in E-filing Corporate Tax Returns One important caveat: if fixing the return requires changing any of the financial figures that appeared on the original Form 8879-S, the officer must review and sign a new authorization reflecting the corrected amounts before the ERO retransmits.
How Long to Keep the Signed Form
The signed Form 8879-S must be retained for three years from the return due date or the date the IRS received the electronic return, whichever is later.1Internal Revenue Service. Form 8879-S – IRS e-file Signature Authorization for Form 1120-S So a Form 8879-S covering a return due March 15, 2026, has to be kept at least until March 15, 2029. If that same return were transmitted late, on September 15, 2026, the three-year clock would run from the later received date instead.
Either the corporation or the ERO can be the custodian, depending on their engagement terms. Electronic storage is fine so long as the system prevents unauthorized alteration and can produce legible copies on demand.7Internal Revenue Service. Revenue Procedure 97-22 If the IRS ever questions whether the corporation authorized the filing, the signed form is the proof.
Deadline and Extensions
Form 8879-S has no separate filing deadline. It just has to be signed before the ERO transmits the return. Form 1120-S itself is due on the 15th day of the third month after the tax year ends, which is March 15 for calendar-year S corporations. Filing Form 7004 extends the return deadline by six months, to September 15.8Internal Revenue Service. Publication 509 (2026), Tax Calendars
An extension of time to file is not an extension of time to pay. If the corporation owes tax, interest and penalties begin accruing after the original March 15 due date regardless of any extension. The electronic funds withdrawal authorization built into Form 8879-S can help here, letting the corporation schedule the payment at the moment of filing rather than mailing a check separately.