What the IRS will change after year end, and what it will not
The Accounts Management manual is categorical: "Adjustments on Form 945-X can only be made if they are the result of an administrative error" (IRM 21.7.2.4.8.1, Jan. 15, 2025), and "Even if income tax or BUWH was erroneously withheld, it cannot be corrected in a subsequent year. This includes erroneous withholding on IRAs" (IRM 21.7.2.4.8.1). The backup-withholding section repeats it: "Tax erroneously withheld does not constitute an administrative error" (IRM 21.7.2.4.8.3, Oct. 1, 2018).
What an administrative error is. "Administrative errors are mistakes in reporting which do not change the amount of income tax, BUWH, or Additional Medicare Tax (AdMT) actually withheld from wages or payments" (IRM 21.7.2.4.4.3.1, Oct. 1, 2015). The manual's examples are an addition error ($7,500 withheld and shown on the W-2s, $7,900 reported on the return) and a transposition ($3,600 withheld, $6,300 reported). Its counter-example is the one payers try: withholding $3,700 when $3,400 was right "due to an error in recording the number of allowances" and showing $3,700 on the W-2 "would not constitute an administrative error and the claim would not be allowable" (IRM 21.7.2.4.4.3.1). Translated to backup withholding: if you withheld 24% from a vendor who had in fact given you a valid W-9, and the 1099 shows the amount withheld, the Form 945-X decrease will be denied. One listed exception: withholding on a payment "mailed to an individual who did not have the ability or legal right to receive the payment in the year the tax was withheld," returned undeliverable, is administrative and is reported in the year actually received (IRM 21.7.2.4.4.3.1).
What the denial says. A prior-year decrease that is not an administrative error is disallowed with Letter 105C or 106C carrying this paragraph: "Amounts reported as income tax withheld, backup withholding, or Additional Medicare Tax withheld in a prior year cannot be changed unless it is to correct an administrative error, Section 3509 applies, or as the result of an examination. An administrative error occurs if the amount you entered on your tax return is not the amount you actually withheld" (IRM 21.7.2.4.4.3 row 4, Oct. 1, 2015). A prior-year increase that is not administrative is processed anyway, with Letter 4384C telling you that you "may file a new Form [specify] to request a refund or credit of the tax reported in error" if the increase itself was a mistake (row 6).
What the payee does instead. The money is not lost; it belongs to the payee as a credit. Before year end, "the payor should report only the correct amount of BUWH on their Form 945" after refunding the payee (IRM 21.7.2.4.8.3). After year end the payee claims it: a private foundation on Form 990-PF, a 501(a) organization or IRA plan on Form 990-T, and "A non-exempt entity required to file an income tax return" on that return (IRM 21.7.2.4.8.3). Partnerships and S corporations cannot: "Reject any claim received on Form 843, Form 1120-S, or Form 1065. Explain that the withholding must be claimed on an individual income tax return" by the partners or shareholders through the K-1 (IRM 21.7.4.4.10, Oct. 1, 2024). Governments and foreign governments exempt under IRC 3406(g)(1) file Form 843 with a signed statement from each payor giving the EIN, amount and date withheld and confirming the payor "did not repay or reimburse the recipient and will not claim an adjustment for the amount on Form 945"; the IRS then reduces the payor's Form 945 and issues the payee a manual refund with interest from the Form 945 due date (IRM 21.7.2.4.8.3 row 3). "If a payee files a Form 843 for tax withheld before the end of the tax year, advise the payee to seek reimbursement from the payor" (IRM 21.7.2.4.8.3 Note).
Three more rules from the same section. "The amount withheld must be reported on Form 945-X under the same EIN as was actually used to do the withholding. Withholding amounts cannot be transferred or delegated to different EINs, unless such action involves a successor employer"; the mutual-fund practice of the year-end transfer agent reporting the whole year's withholding "CANNOT be done" and such requests are denied with a 105C or 106C (IRM 21.7.2.4.8.1, Jan. 15, 2025). If neither box in Part 1 is checked, or both are, on a decrease, the assistor makes two phone attempts and otherwise processes it as an adjusted return (IRM 21.7.2.4.8.1 Note). And an adjusted return "filed within 90 days of the expiration of the period of limitations" is converted to a claim with Letter 4384C (IRM 21.7.2.4.8.1.1, May 10, 2023). The interest-free rule for increases is the one this page opened with: TC 298 only "if the Form 945-X was filed by the due date of the return for the period in which the taxpayer discovered the reporting error" with the discovery date given; the manual's example is an error found February 5, 2025 and a 945-X received March 4, 2025, with interest computed from March 4 (IRM 21.7.2.4.8.1.3, Mar. 10, 2025).
The interest-free rule
Form 945-X is an adjusted return under IRC 6205. An underpayment reported on it is an interest-free adjustment if the X-form is filed "by the due date of the return period in which the error was ascertained" and the additional tax is paid with it (IRM 20.1.2.3.9(2)). For Form 945, whose return period is the calendar year, that means: an error found in any month of 2026 is corrected interest-free if the 945-X is filed and paid by February 1, 2027 (January 31, 2027 is a Sunday). An error found on January 15, 2027 belongs to the 2027 period and has until the start of February 2028.
The X-form has no due date of its own. "Since the above returns are not 'required' to be filed by a specific due date (except to qualify for an interest-free adjustment), the penalty for filing late does not apply to these returns" (IRM 20.1.2.3.9(3)). There is never a failure-to-file penalty on a 945-X.
Why a timely X-form is exempt from the deposit rules
The question a payer worries about is the deposit penalty: the withholding should have been deposited monthly or semiweekly in the year it was withheld, and it was not. The regulation answers it. Treas. Reg. 31.6302-1(c)(7) exempts a timely adjusted return from the monthly and semiweekly deposit rules on the increase; the IRM applies it as follows: "If the amount of TC 298/308 interest-free adjustment is paid by the received date of the adjusted return ... the amount timely paid will be deemed to have been timely deposited" (IRM 20.1.4.21.5(2)). The payment "may be made by a check or money order with the adjusted return, by EFT, or by other methods," so paying with the return does not trigger the 10% avoidance penalty that normally attaches to a required deposit paid any other way (IRM 20.1.4.21.5(3)).
The consequence is that a payer who finds in September that March's backup withholding was under-deposited by $8,000 owes, if it files and pays a 945-X before the next February 1, exactly $8,000. No deposit penalty, no late-payment penalty, no interest.
Three scenarios
| What you do | Failure to deposit (IRC 6656) | Failure to pay (IRC 6651(a)(2)) | Failure to file | Interest |
|---|---|---|---|---|
| 945-X filed by the due date of the discovery period, tax paid with it | None: the amount paid is deemed timely deposited | None | Never applies to a 945-X | None (IRC 6205) |
| 945-X filed by that date, tax not paid with it | 10% of the unpaid amount (IRM 20.1.4.21.5(4)) | 0.5% per month from the filing date, 1% after a levy notice, to 25% (IRM 20.1.2.3.9(2)) | None | From the date the X-form was filed |
| 945-X filed after that date | Recomputed on the whole year against a corrected liability schedule: the original deposits are tested against the corrected liabilities, and the shortfall is late from the original deposit due dates, up to 10% plus 5% after notice (IRM 20.1.4.21.5(6)) | From the original return due date | None | From the original return due date (IRC 6205 treatment lost) |
The middle row is the trap. Filing the X-form on time but sending the payment separately later loses the deposit exemption on the unpaid amount; "If the adjusted return is timely but the tax is not paid with it, the amount of the unpaid tax is subject to a 10 percent FTD penalty." Pay with the return, or by EFTPS the same day.
When the X-form is late
An X-form filed after the due date of the discovery period is processed as an ordinary adjustment (TC 290), not an interest-free one, and "a corrected ROFTL for the new total tax is required to test deposit timeliness on the whole year" (IRM 20.1.4.21.5(6); 20.1.4.21.5.1(3)). The corrected schedule puts the additional liability on the dates it was actually withheld, or should have been, and the deposits made during the year are re-applied against the corrected totals. Any shortfall is late from the original due dates. The Form 945 deposit penalty calculator computes that: enter the corrected liabilities and the deposits actually made.
An increase on an X-form filed late is also where the IRS default application of deposits matters most, since the re-applied deposits go to the most recent periods first and can leave an early-year liability entirely uncovered. The IRC 6656(e) designation is available within 90 days of the resulting penalty notice.
The liability schedule
An amended Form 945-A is "generally not required" with an X-form, with two exceptions: when the original schedule was invalid (blank, negative, or not agreeing with the return), and when a decrease is being reported on a year where a penalty was charged on the higher tax (IRM 20.1.4.21.5.1(1) and (2)). On a decrease where the penalty had been averaged because no good schedule existed, the IRS simply re-averages the lower tax; where the penalty was computed on the higher tax, the net penalty after the decrease is capped at 10% of the net tax plus 5% of any net tax still unpaid, a floor worth checking a CP 210 against (IRM 20.1.4.21.3(13)).
A corrected or first-time schedule received after a penalty was assessed "must be considered and the FTD penalty adjusted" (IRM 20.1.4.18.2), but note the reverse: a revised schedule triggers a full recompute "even if no penalty was originally assessed" (IRM 20.1.4.21.2(2)). Correcting a 945-A can increase the penalty when the corrected dates are earlier than the ones originally reported. Oral requests to change dates or amounts on the schedule are not accepted; a signature is required only when the total tax changes (IRM 20.1.4.21.2(3)).
Box 1 or Box 2, and the claim rules
The employment-tax examination manual says the checkbox on Part 1 does not change how the case is worked, "it does affect the final processing of the case" (IRM 4.23.13.1.1(7), 4.23.13.7, July 1, 2024). A Box 1 (adjusted return) credit "MUST be moved to the period in which the 'X' adjusted return was filed": the examiner enters Hold Code 2 to stop any refund and the credit moves by TC 830 from the corrected year to TC 710 in the year the 945-X was filed (Exhibit 4.23.13-2). "Adjusted returns can not result in a refund issued to the taxpayer" (IRM 4.23.13.1.6). For a Form 945 filer, the period in which the X was filed is the current calendar year, so a Box 1 prior-year overpayment only ever appears as a credit against current-year backup withholding. If you want money back, that is Box 2, a claim.
The 90-day rule. An adjusted return filed "within 90 days of the expiration of the period of limitations on credit or refund (RSED) ... must be converted to a claim for refund," citing Treas. Reg. 31.6413(a)-2(d)(2) and Rev. Rul. 2009-39 (IRM 4.23.13.2.2(3), 4.23.13.7(4), July 1, 2024). Filing the X form does not extend any statute. Claims are worked as priority because "If the IRS does not act on a claim for refund within six months from the filing date of the claim, the taxpayer is permitted to file a refund suit" (IRM 4.23.13.2(2)).
"FITW, BUWH, and AdMT cannot be corrected after the close of the calendar year unless the issue constitutes an administrative error. This is true even if FITW, BUWH, or AdMT was erroneously withheld" (IRM 4.23.13.2.1(3), July 1, 2024). The prior-year claim route exists "only to the extent the amount of the FITW, BUWH, and AdMT overpayment was not actually deducted and withheld from a payee."
The rule behind that is IRC 6414: "IRC 6414 permits refunds of FITW to an employer only to the extent the amount of the FITW overpayment was not actually deducted and withheld from an employee" (IRM 4.23.13.10(5), July 1, 2024), and backup withholding is the same chapter of withholding. A same-year error is fixed by repaying or reimbursing the payee before the year closes (Treas. Reg. 31.6413(a)-1; IRM 4.23.13.10(4)), where "reimburses" means "applying the overwithheld amount against taxes to be withheld on future wages" (IRM 4.23.13.10(3) Note), and the payer "must obtain and retain the written receipt of the employee showing the date and amount of the repayment or the evidence of reimbursement" (IRM 4.23.13.10(6)). Repayment or consent need not precede filing, "However, the employer must repay or reimburse its employees or obtain the employees' consents before the IRS can grant the claim" (IRM 4.23.13.10(10)). A prior-year 945-X for backup withholding that was actually taken from the payee's payment is disallowable on its face; the payee's outlet is Form 1040 (IRM 4.23.13.2.1(4)). Examiners "secure copies from the employer and review them to ensure compliance" with the Part 1 certifications (IRM 4.23.13.2.1(2)).
The statute runs from April 15. Returns reporting withholding "filed before April 15 of the succeeding calendar year are 'deemed filed' on April 15" under IRC 6501(b)(2) and 6513(c) (IRM 4.23.13.2.2, July 1, 2024). Both the three-year assessment statute and the three-year refund statute on a timely Form 945 run from April 15 of the following year, not from January 31; the Accounts Management manual states the same rule for the assessment side (IRM 21.7.9.4.1.1.2(2), Oct. 6, 2025). The refund statute's other prong, two years from payment, and the cap on refunds outside three years to tax paid in the prior two years (IRC 6511(b)(2)(B)) apply as usual. "If the Form 94x-X is an abatement, the RSED does not apply" (IRM 4.23.13.2.2(4)).
The deposit penalty does not follow the claim. When a claim reduces tax and a failure-to-deposit penalty was assessed, the examiner "should inform the taxpayer to submit ... Form 945-A, Annual Record of Federal Tax Liability, as appropriate, so the Failure to Deposit (FTD) penalty can be recomputed at the Campus" (IRM 4.23.13.3.3.1(4) Note, July 1, 2024). Send a Form 945-A with the corrected liabilities with the 945-X; the recomputation is not automatic.
Filing method and entity side effects. "As of June 2024, Form 941-X, Form 943-X, and Form 945-X may be filed using MeF" (IRM 21.7.9.4.1.2.2, Oct. 1, 2026). The address on an amended return is adopted as the address of record under Rev. Proc. 2010-16 unless a later change is already on file, and "Form 8655, Reporting Agent Authorization, does not authorize a reporting agent filer to request an address change for the taxpayer (client)" (IRM 21.7.9.4.1(8)-(9) Note, Oct. 1, 2026). Put the address of record on the 945-X unless you mean to change it, and do not expect a reporting agent's 945-X to change it. For what happens when a second plain Form 945 is filed instead of a 945-X, see the second Form 945 page.
Questions people ask
We found the error in December. Do we have until February 1?
Yes. The discovery period is the calendar year in which you found it, so an error found on December 20, 2026 is corrected interest-free by February 1, 2027, the same date as an error found in March.
We never withheld at all on a payee we should have. Is that a 945-X?
If you are paying the tax yourself under IRC 3403 because you failed to withhold, yes, it is reported as an increase on the 945-X for the year of the payments, and the timing rules above apply. If the payee has since reported and paid the tax, Form 4669 from the payee relieves you of the tax (not the penalties or interest); see the Form 4669 and 4670 guide.
Does the interest-free rule cover a decrease?
A decrease is a refund or credit claim on the same form; interest runs in your favor from the overpayment date under the normal rules. The timing rule on this page is about underpayments.
Can we use First Time Abate on the penalties in the second and third rows?
Form 945 is eligible for First Time Abate on failure-to-deposit and failure-to-pay penalties if the prior three years are clean and all returns are filed, unlike the 1099 penalties themselves. See First Time Abate and the relief order.