1099 backup withholding is a flat 24% that a payer must deduct from certain payments reported on a Form 1099 and send directly to the IRS, and it applies only when a payee’s Taxpayer Identification Number is missing, wrong, or has been flagged by the IRS. It isn’t a penalty or an extra tax. For the payee, the withheld amount is a prepayment of income tax that comes back as a credit at filing time. For the payer, it’s a compliance duty with real personal liability if ignored. The rest of this article walks through what sets it off, which payments it touches, how a payee stops it, and what a payer has to do once it starts.
What Triggers Backup Withholding
Federal law lists four situations that require a payer to start withholding 24%. Two apply to any reportable 1099 payment. Two apply only to interest and dividend income.
The first, and the most common, is a missing or obviously wrong TIN. If a contractor or other payee never returns a completed Form W-9, or the number they give has fewer than nine digits, too many digits, or contains letters, the payer must withhold starting with the very first payment. There is no notice period for this trigger.
The second is a TIN mismatch flagged by the IRS. The IRS sends the payer a CP2100 or CP2100A notice listing payees whose names and TINs don’t match its records. The payer sends those payees a “B-Notice,” and if the payee doesn’t respond with corrected information, withholding must begin no later than 30 business days after the notice.
The remaining two triggers cover interest and dividend income only. One is an IRS directive to the payer that a particular payee has a history of underreporting investment income; withholding starts 30 days after the payer receives that directive. The other is a payee’s failure to certify on Form W-9 that they aren’t currently subject to backup withholding for underreporting. Neither applies to independent contractors or ordinary 1099-NEC payments.
Which 1099 Payments It Applies To
Backup withholding can reach most payments reported on a 1099-series form. The categories the IRS identifies include:
- Nonemployee compensation on Form 1099-NEC (contractor fees, commissions)
- Interest on Form 1099-INT
- Dividends on Form 1099-DIV
- Rents, royalties, attorney gross proceeds, and other income on Form 1099-MISC
- Broker and barter proceeds on Form 1099-B
- Payment card and third-party network transactions on Form 1099-K
- Certain government payments on Form 1099-G
- Gambling winnings on Form W-2G that aren’t already subject to regular gambling withholding
If a payment gets reported on a 1099, backup withholding is on the table whenever a trigger condition exists.
If You’re the Payee: Stopping It and Getting the Money Back
The 24% isn’t lost. It’s sitting in your IRS account as a prepayment of your income tax, the same way W-2 withholding sits there for an employee. The payer will report the withheld total in Box 4 of your Form 1099. When you file Form 1040, you enter that amount on the federal income tax withheld line, and it reduces your balance due dollar for dollar. If it exceeds what you owe, the excess comes back as a refund. Keep the 1099 with your tax records as proof the money was paid on your behalf.
Prevent It in the First Place
Give every payer a properly completed Form W-9 before your first payment. Enter your correct TIN, sign Part II, and leave the backup withholding certification intact unless the IRS has actually notified you about underreporting. That single form handles two of the four triggers.
Fix a Mismatched TIN
If a payer sends you a B-Notice saying your TIN doesn’t match IRS records, respond fast. A first B-Notice is resolved by returning a properly signed W-9 with corrected information. A second B-Notice within three years requires more: a copy of your Social Security card, or an IRS Letter 147C confirming your name and EIN. Once the payer has your corrected information, withholding should stop within 30 days.
Resolve an Underreporting Notice
Withholding triggered by underreported interest or dividends is harder to lift. The IRS has to make a formal determination that one of several conditions is met: there was no actual underreporting, you’ve corrected it and paid all tax, penalties, and interest, continued withholding would cause undue hardship, or there’s a genuine dispute over whether underreporting occurred. Once determined, the IRS issues you a written certification and separately notifies your payers to stop. The timing depends on when the IRS acts, and in some cases the determination isn’t finalized until December 1 of the year it’s made.
If You’re the Payer: The B-Notice Process, Deposits, and Reporting
Most payers first meet backup withholding when a CP2100 or CP2100A arrives. The CP2100 goes to payers who filed 50 or more information returns with errors; the CP2100A covers fewer. The content is the same: a list of payees whose TINs don’t match IRS records, and instructions for what to do next.
Sending a First B-Notice
Before contacting the payee, compare the IRS listing against your own records. A data-entry error on your side can be fixed without involving the payee at all. If your records match what the payee originally provided, send a First B-Notice along with a blank Form W-9. The payee must return a properly completed and signed W-9. If no corrected TIN arrives, begin withholding no later than 30 business days after the CP2100 or CP2100A date, or the date you received it, whichever is later.
Sending a Second B-Notice
If the same payee appears on another CP2100 or CP2100A within three years, a W-9 alone is not enough. Send a Second B-Notice and require a copy of the payee’s Social Security card or an IRS Letter 147C. The higher bar reflects that the TIN has been wrong twice.
Depositing the Withheld Funds
The calculation is simple: 24% of the gross reportable payment. Pay a contractor $5,000, withhold $1,200, send $3,800 to the contractor, and the $1,200 goes to the IRS. Deposits run through the Electronic Federal Tax Payment System (EFTPS), the same channel used for payroll tax deposits. ACH credit transfers and same-day wire payments through your bank are alternatives, though they may carry fees.
Deposit frequency depends on your total Form 945 liability from two years prior. A 2024 Form 945 liability of $50,000 or less makes you a monthly depositor for 2026, with deposits due by the 15th of the following month. Above $50,000, you’re on a semi-weekly schedule. One rule overrides both: if accumulated non-payroll withholding hits $100,000 during a deposit period, the deposit is due the next business day. Late deposits carry penalties that start at 2% and rise to 15% depending on how far past due the payment is; only the highest applicable rate applies, but interest accrues until everything is paid.
Reporting on Forms 1099 and Form 945
Report each payee’s withheld total in Box 4 of the appropriate Form 1099 (1099-NEC for contractors, 1099-MISC for rent and royalties, and so on). Furnish the 1099 to the payee by January 31. Filing deadlines with the IRS vary by form: Form 1099-NEC is due January 31; Form 1099-MISC is due February 28 on paper or March 31 electronically.
Form 945 is the annual reconciliation of all non-payroll federal income tax withholding, including backup withholding, pension withholding, and gambling withholding. The Form 945 total must equal the sum of Box 4 amounts across every information return you issued. File by January 31, with an automatic extension to February 10 if every deposit during the year was on time.
What Happens If a Payer Doesn’t Withhold
A payer who was required to backup withhold and didn’t can become personally liable for the tax that should have been collected. The IRS treats withheld taxes as trust fund money that belongs to the government from the moment it should have been deducted, whether or not it actually was. Under federal law, any person responsible for collecting and paying over withheld taxes who willfully fails to do so faces a penalty equal to the full amount of the uncollected tax. In a small business, “responsible person” generally means owners, officers, or anyone with authority over financial decisions, and this personal liability isn’t blocked by an LLC or corporation. Add the failure-to-deposit penalties and interest on any amounts that were withheld but not remitted, and ignoring backup withholding becomes one of the more expensive compliance mistakes a small business can make.
Foreign Payees
Backup withholding doesn’t apply to foreign individuals, who fall under a separate withholding regime. A foreign payee establishes that status by providing Form W-8BEN instead of Form W-9. A valid W-8BEN on file takes the payee out of backup withholding, though other withholding rules may still apply. If someone claims to be foreign but won’t provide the W-8BEN, treat them as a payee without a TIN and start withholding at 24%.