Backup Withholding on 1099 Payments: The 24% Rule Explained

TL;DR: If you pay a sub $600 or more in a tax year without a valid W-9 on file, IRS rules require you to withhold 24% of the payment as backup withholding and remit it on Form 945. Four triggers apply: no TIN, an invalid TIN flagged by a CP2100 notice, IRS notification of underreporting, or a missing W-9 certification, and the GC (not the sub) owes the unpaid tax plus penalties.

Here's an IRS rule most GCs don't know about: if you pay a subcontractor $600 or more and you don't have a valid W-9 on file, you're legally required to withhold 24% of the payment as backup withholding and remit it to the IRS.

Miss this rule, and the IRS comes for you (not the sub) for the unpaid withholding, plus penalties, plus interest. This post covers exactly how backup withholding works, when it applies, and how to make sure you never need to use it.

What Is Backup Withholding?

Backup withholding is a mechanism the IRS uses to collect tax from payees who haven't given the payer their correct taxpayer information. The idea is simple: if the IRS can't match a 1099 to a valid TIN in its records, the IRS wants to make sure they still collect the tax owed on that income. So they require the payer (you, the GC) to withhold a percentage upfront and send it to the IRS.

The rate is currently 24% of the gross payment. This rate is set by statute and has been 24% since 2018.

When Does Backup Withholding Apply?

There are four main triggers. Any one of them is enough.

Trigger 1: No TIN Provided

The subcontractor hasn't given you a W-9 at all, or the W-9 they gave you is missing their TIN (SSN, EIN, or ITIN). This is the most common trigger for GCs. You're paying a sub who just never got around to sending their W-9.

Trigger 2: Invalid TIN

The sub provided a TIN that doesn't match IRS records. You may not know this until you file a 1099 and the IRS sends you a "CP2100" or "CP2100A" notice telling you the TIN doesn't match. Once you receive that notice, you must start backup withholding on future payments until the sub provides a corrected TIN.

Trigger 3: IRS Notification of Underreported Income

The IRS has notified the payer that the payee underreported income on previous returns. Rare for subcontractor relationships but possible.

Trigger 4: Failure to Certify on W-9

The W-9 has a certification section at the bottom where the sub attests they're not subject to backup withholding. If the sub leaves that section blank or crosses it out, backup withholding applies.

How Backup Withholding Works in Practice

Let's say you owe a sub $5,000 for framing work and you don't have a valid W-9.

Without backup withholding (wrong), you write a check for $5,000 and move on.

With backup withholding (correct):

1. Calculate the withholding: $5,000 × 24% = $1,200
2. Pay the sub: $5,000 − $1,200 = $3,800
3. Deposit the $1,200 with the IRS using their electronic federal tax payment system (EFTPS)
4. Report the withholding on Form 945 (Annual Return of Withheld Federal Income Tax) at year-end
5. Report the withholding on the sub's 1099-NEC in Box 4 when you file in January

You end up paying out the same total ($5,000 to the sub + IRS), but $1,200 of it goes to the IRS on the sub's behalf. The sub later gets credit for that $1,200 on their own tax return.

Deposit Rules

Backup withholding deposits follow the same schedule as payroll tax deposits:

• Monthly deposit schedule: If your total backup withholding for the year is $50,000 or less, you deposit by the 15th of the following month.
• Semi-weekly deposit schedule: If you withheld more than $50,000 in the prior year, deposits are due within a few business days of each payment.
• $100,000 next-day rule: If you accumulate $100,000 or more of withholding on any day, you must deposit by the next business day.

For most GCs who occasionally withhold small amounts, the monthly schedule applies and is manageable. The problem is that it's a compliance headache you don't want. One more deadline, one more form, one more place to make mistakes.

Why This Rule Is a Trap for GCs

Backup withholding is a trap because:

1. Nobody tells you about it. It's buried in IRS Publication 1281 and Form W-9 instructions. Most GCs have never heard of it until a CPA or auditor brings it up.
2. The penalty structure punishes the payer, not the payee. If you don't withhold and the IRS later determines you should have, you owe the 24%. Plus penalties. Even if the sub paid their own taxes properly. You can't "undo" it.
3. It's a sign of bigger problems. If you're paying subs without W-9s, you probably have compliance gaps elsewhere too. Uninsured subs, missing licenses, etc.
4. It's avoidable. The fix is free and takes five minutes: collect the W-9 before you cut the check.

Penalties for Not Withholding

If the IRS determines you should have been backup withholding and weren't, you face:

• The unpaid withholding itself. The IRS can assess you for the full 24% you should have withheld. You can try to recover from the sub, but good luck.
• Failure to deposit penalty. Up to 15% of the underpayment.
• Interest. Accruing from the original deposit due date.
• Failure to file information returns penalty. Separate penalty for improperly filed 1099s. Up to $330 per form.

On a single $100,000 sub payment made without a W-9, the IRS exposure can easily be $30,000+ in unpaid withholding and penalties.

How to Avoid This Entirely

The rule is simple: never pay a subcontractor without a valid W-9 on file first.

Build this into your AP workflow as a hard gate:

1. New sub is added to the system
2. Sub is sent a W-9 request immediately
3. Sub cannot be paid until the W-9 is uploaded and validated
4. AP system blocks payment requests for subs without a W-9

This eliminates backup withholding situations entirely. No W-9, no payment. Sub figures it out fast.

What to Do If You Already Paid a Sub Without a W-9

Don't panic, but act fast:

1. Request the W-9 immediately. Most subs will provide it within a day or two when they know you can't issue a 1099 without it.
2. If they refuse or go silent: Start backup withholding on all future payments. Withhold 24% of every check until you have a valid W-9.
3. For past payments without withholding: Talk to your CPA. You may need to amend filings or face backup assessment. Don't try to self-correct without guidance.
4. File a proper 1099-NEC with whatever TIN information you have. An imperfect 1099 filed on time is better than a perfect one filed late (or never).

How PaperBoss Prevents This

PaperBoss makes backup withholding situations impossible. When you onboard a new sub, the first thing PaperBoss does is send a W-9 upload request. The sub uploads the W-9 via a secure link (no account needed), and until that W-9 is on file, the sub's record is flagged as "W-9 missing."

You integrate PaperBoss into your AP workflow as a rule: don't issue a check to any sub whose PaperBoss record isn't W-9 compliant. That one rule eliminates every backup withholding trigger before it happens.

And when January arrives, PaperBoss exports a clean CSV with every sub's W-9 data for straightforward 1099-NEC filing through Track1099, Tax1099, or your accountant's tool.

Start a 14-day free trial, no credit card required.

Frequently Asked Questions

Does backup withholding apply to corporations?

Generally no, because payments to corporations usually aren't reportable on 1099-NEC in the first place, but if the sub claims corporate status and the IRS later determines the status was wrong (or you can't verify it), backup withholding can apply.

Is backup withholding the same as tax withholding for employees?

No. Employee tax withholding is based on W-4 forms and IRS withholding tables, varies by income level, and covers both federal income tax and FICA. Backup withholding is a flat 24% on 1099 payments as a result of incomplete tax documentation.

Can I charge the backup withholding back to the sub?

Yes, in the sense that the sub receives less money (you withheld 24%). No, in the sense that you can't "charge the withheld tax" as a separate fee. The sub's lower paycheck is the mechanism.

How do I deposit backup withholding to the IRS?

Through EFTPS (Electronic Federal Tax Payment System. Eftps.gov). You designate the deposit as "Federal Income Tax Withheld (Non-Payroll)". Form 945 deposits.

What form do I file to report backup withholding annually?

Form 945. "Annual Return of Withheld Federal Income Tax". Due January 31 of the following year.

Does backup withholding apply to gross payments or net?

Gross payments. Calculate 24% of the total invoice amount before any deductions.

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This article is for educational purposes only and does not constitute tax or legal advice. Consult a qualified CPA for guidance on backup withholding and 1099 compliance.