The backup withholding examination, as the IRS runs it

What the examiner is examining

The four triggers for backup withholding under IRC 3406(a) are a missing TIN, an IRS notice that the TIN is incorrect, notified payee underreporting and a certification failure, and the manual tells examiners that "Generally, an employment tax examiner will encounter backup withholding issues when either (a) or (b) occurs" (IRM 4.23.8.14 Note, Apr. 17, 2024). The rate "effective January 1, 2018, is 24 percent," it applies to "most kinds of payments that are reported on Forms 1099-MISC and 1099-NEC," and "The examiner will compute backup withholding tax on an annual basis whether the payments are sporadic over the year or by a single lump sum" (IRM 4.23.8.14). Backup withholding "is treated as withholding on wages per IRC 3406(h)(10)," and a payee whose foreign or U.S. status cannot be determined is subject to backup withholding, not nonresident alien withholding, under the presumption rules (IRM 4.23.8.14).

What the examiner has before the first meeting

"The examiner should request a payer master file transcript (CC PMFOL) for a summary of the payor's information returns by year, type, and dollar amount. A PMFOLB shows the number of Forms 1099 filed with missing, unassigned, and mismatched TINs as well as the years that payor received a CP2100 Notice" (IRM 4.23.8.14.2, Apr. 17, 2024). The examiner therefore knows, before asking you anything, how many of your 1099s had bad TINs in each year and which years you were sent a CP2100. The PMFOL guide shows the screens.

If PMFOLB shows a CP2100, the examiner can order a recreate of the notice from Electronic Products and Services Support by fax or email, allowing "four to six weeks" (longer for notices with 250 or more payees, which arrive on an encrypted CD) (IRM 4.23.8.14.2.1, Apr. 17, 2024). The recreate is the list the examiner tests your B-Notice mailings against, name by name. If you cannot produce your own copy of a CP2100 from three years ago, assume the examiner can.

Worker classification comes first

"Before determining whether a payor is subject to backup withholding, examiners must first consider whether a potential worker classification issue exists with regard to the payees. If the payees are determined to be employees, backup withholding is not applicable even if the payor would have been subject to backup withholding based on failing to secure the payees' TINs. Failure to consider the worker classification issue first may provide the payor with a prior audit safe haven under section 530 for subsequent year" (IRM 4.23.8.14.2, Apr. 17, 2024). The order protects the IRS, not the payer: an examiner who assessed backup withholding without looking at classification would hand the business a section 530 prior-audit safe haven for later years.

Two reminders follow. "The non-filing or late filing of information returns eliminates the section 530 safe haven for that year," and "If a worker is later determined to not be an employee (for example, in an Appeals determination), backup withholding should be considered as an alternate position in a worker classification examination" (IRM 4.23.8.14.2 Reminders). The section 530 guide covers the first; the second means a classification win on appeal reopens the 24% question for every contractor whose TIN was never on file.

How the amount is fixed

The computation has two start dates. For a missing TIN, withholding was required from the first payment made without one, and the manual's PMTA 2023-03 reminder removes the argument that no CP2100 was ever received. For an incorrect TIN flagged on a CP2100, the clock is the notice's: the payee "should return the Form W-9 (or acceptable substitution) within 15 business days, or within 30 business days of the date of the CP2100 Notice," and "If the payee does not provide the Form W-9 ... within 30 business days, the payor must begin backup withholding by the 30th business day after the date of the CP2100 Notice" (IRM 4.23.8.14.1, Apr. 17, 2024).

The examiner's version of the B-Notice rules matches Publication 1281 with one useful precision on the second notice: "a copy of a social security card will serve as validation from the SSA," "Letter 147-C ... serves as validation for a Business Master File (BMF) taxpayer," and "a TIN certified on a Form W-9 is not sufficient to stop or prevent backup withholding for a second notice." A card is accepted if its name and SSN differ from the notice "or" it "is dated no earlier than six months prior to the date of the 'second B Notice'" (IRM 4.23.8.14.1). The manual also restates the no-notice rule: where an account on the CP2100 does not match your records "No 'B' Notice is required," only a correction of your own records (IRM 4.23.8.14.1 Note). Those are the facts the examiner expects your solicitation log to show for each name.

What the exam tests, in the manual's words, is "compliance with the CP2100 process": whether each name on each notice got the right B-Notice within 15 business days, whether withholding started by business day 30 where no W-9 came back, whether second-notice accounts were held to the SSA-card or 147C standard, and whether payments to payees who never furnished a TIN were withheld on from the start. Each failure is 24% of the payments from the date withholding should have begun to the date it did, or to year end.

Form 4668-B and what follows

"All references to employment tax procedures for the withholding of income tax on wages, except for special rules related to IRC 3509 rates or CSP, apply to backup withholding" (IRM 4.23.8.14.2, Apr. 17, 2024). The reduced IRC 3509 rates and the Classification Settlement Program, which soften worker-reclassification assessments, are not available for backup withholding. The report is "Form 4668-B, Report of Examination of Withheld Federal Income Tax Reported on Forms 1099 and W-2G," at "24 percent effective 2018," with a separate Form 4668 if other employment taxes are adjusted (IRM 4.23.8.14.2; 21.7.2.5.8 Note, Jan. 14, 2015). The agreement form is Form 2504, and "An error is considered ascertained on the date the signed Form 2504 or Form 2504-WC is received by the IRS. Therefore, the additional tax must be paid at the time the signed Form 2504 is received for the assessment to be completely interest-free" (IRM 21.7.2.5.8). Sign and pay on the same day, or interest runs.

The assessment posts to the Form 945 module for the year (MFT 16), and from there the ordinary collection sequence applies: the bill, CP504, then the levy notice. Because backup withholding is employment tax, a payer that has previously requested a collection due process hearing on employment taxes within two years can face a levy without a new pre-levy hearing under the disqualified employment tax levy rules (IRM 5.19.4.3.1.1, June 1, 2020). One Form 945 fight makes the next one faster.

Forms 4669 and 4670

"The backup withholding assessment under IRC 3406 is subject to the abatement provisions of IRC 3402(d)" (IRM 4.23.8.14.2, Apr. 17, 2024), and the Accounts Management manual confirms that "IRC 3402(d) relief also applies to Exam assessments of backup withholding" (IRM 21.7.2.5.8, Jan. 14, 2015). The mechanism is a signed Form 4669, Statement of Payments Received, from each payee for each year, "signed under the penalties of perjury," with "every line item completed (Part 1 by the payor and Part 2 by the payee)," transmitted on a Form 4670 prepared by the payor; "If any information is omitted from a Form 4669, it must be returned to the payor for correction, as it is the responsibility of the payor to obtain properly completed forms from payees" (IRM 4.23.8.14.2). Examiners "are authorized to accept and consider any Form 4669 submitted before the case is closed from the group."

After the group closes the case the route depends on whether the tax was paid: "If the examination is closed but the tax has not been paid, advise the taxpayer to submit the completed Forms 4669 and Form 4670 to the campus where the Form 945 is filed, along with a copy of the Form 4668-B"; "If the examination is closed and the tax paid, advise the taxpayer to submit a Form 945-X ... attaching the completed Forms 4669 and Form 4670, along with a copy of the Form 4668-B" (IRM 4.23.8.14.2). The relief covers the tax the payee already paid on the income; it never covers penalties or interest, and it never covers a payee you cannot find. The Form 4669 and 4670 guide covers the package and the rejection checklist.

Delinquent 1099s secured in the exam

"The examiner should secure any delinquent Forms 1099 that were required to be filed during the audit years" (IRM 4.23.8.11.4, Apr. 17, 2024). They go to the campus under a Form 1096 marked in red "Delinquent Returns - Secured by Examination - Penalty Considered," and the examiner must "Evaluate and address whether backup withholding applies when Forms 1099 were required but not filed or furnished and the taxpayer did not have the payee's TIN at the time of making a reportable payment" (IRM 4.23.8.11.4). Recipients "that appear to have high income tax potential for possible income tax under-reporting" are referred on Form 5346 (IRM 4.23.8.11.4); the exam of the payer becomes the lead on the payee.

Securing the returns also starts a clock that was not running before. For a return never filed there is no statute on the IRC 6721 penalty; once delinquent returns are secured the examiner updates the penalty statute "to 3 years from the date that the delinquent returns were secured" (IRM 4.23.8.12 Note, Apr. 17, 2024; 4.23.9.13.6, Oct. 6, 2022). The statute page has the rest of the rules.

If you do not sign Form 2504

An unagreed backup withholding examination ends in a 30-day letter. Backup withholding is not an IRC 7436 worker-classification issue, so the letter is "Letter 950-D, Employment Tax 30-Day Letter: Issued for all non-IRC 7436 employment tax issues," with Form 4668-B, Form 2504 and Publication 5 enclosed (IRM 4.23.22.6, Feb. 27, 2025). Where the same examination also reclassified workers, "Separate 30-day letters are to be issued when both IRC 7436 and non-IRC 7436 issues are present," and the classification side goes out on Letter 950-C with its own path to Letter 3523 and the Tax Court; the backup withholding side does not get Tax Court review, which is why "the examiner should treat the BWH issue as independent and seek a consent to extend the limitations period" and, in a 7436 case, "must immediately assess the backup withholding and suspend collection until after the Tax Court proceeding is concluded" (IRM 4.23.22.11.1).

The response rules are the ordinary examination ones. A protest to Appeals is a "small case request" on Form 13683 where the tax and penalties for each return and period are $25,000 or less, and a formal written protest meeting Publication 5 above that; a deficient protest is returned on Letter 1025-P with time to perfect it (IRM 4.23.22.6, 4.23.22.8.1). Extensions of the 30 days are "granted under reasonable circumstances," normally "for no more than 30 days," by the group manager on Letter 686 (IRM 4.23.22.9, May 16, 2018). Appeals needs "at least 365 days on the statute of limitations when received," so expect to be asked to sign Form SS-10 with the letter (IRM 4.23.22.6). "If the taxpayer does not respond to proposed adjustments involving only non-IRC 7436 issues, the case should be closed unagreed promptly for tax assessment after the 30-day suspense period (including extensions) has expired" (IRM 4.23.22.8.6), and the assessment follows the ordinary collection path. Fast Track Settlement, designed to finish "within 60 days (for SB/SE taxpayers)" with Appeals mediating while the examiner keeps the case, is available before the 30-day letter issues (IRM 4.23.22.4.2). The Appeals guide covers what the conference looks like once the case arrives; agreed cases close with Letter 3382 and, where the tax was not paid, interest "from the date the signed agreement form was received by the IRS" (IRM 4.23.10.6, June 1, 2023).

Questions people ask