Backup Withholding at 24%:
When It Starts and How to Stop

What Is Backup Withholding?

Backup withholding is a federal tax collection mechanism that requires payers to deduct a flat 24% from certain payments and remit that amount to the IRS. It is called "backup" withholding because it serves as a backup to the normal self-reporting system: when the IRS cannot match reported income to a taxpayer because of a missing or incorrect TIN, it forces the payer to withhold taxes directly.

Backup withholding applies to most types of payments reported on 1099 forms, including:

• Non-employee compensation (1099-NEC)
• Rents, royalties, and other income (1099-MISC)
• Interest payments (1099-INT)
• Dividend payments (1099-DIV)
• Payment card and third-party network transactions (1099-K)
• Broker proceeds and barter exchange transactions (1099-B)

The IRS provides a complete overview of backup withholding on its backup withholding page.

What Triggers Backup Withholding?

Backup withholding does not happen automatically with every TIN error. It is triggered by specific events in a defined sequence. Understanding these triggers helps you anticipate and avoid them:

Trigger 1: Payee Fails to Provide a TIN

If a payee does not furnish a TIN (by failing to return a W-9 form) and you make reportable payments, you must begin backup withholding immediately. This is why collecting W-9s at vendor onboarding is not optional -- it is a compliance obligation.

Trigger 2: IRS Notifies You of an Incorrect TIN

When you receive a CP2100 or CP2100A notice, you must send a B-Notice to the affected payees. If a payee does not respond to a First B-Notice within 30 calendar days with a corrected, certified TIN, backup withholding must begin. For a Second B-Notice, withholding must begin immediately.

Trigger 3: IRS Direct Notification (Notice 1446)

In some cases, the IRS sends a direct notification (sometimes called a "C-Notice" or Notice 1446) instructing you to begin backup withholding on a specific payee. This can happen when the payee has underreported income or when the IRS has other reasons to require withholding. You must comply immediately upon receipt.

Trigger 4: Payee Fails to Certify Non-Subject Status

Certain payees must certify that they are not subject to backup withholding (Part II of the W-9). If a payee fails to make this certification, backup withholding applies to interest and dividend payments.

The 24% Rate: How to Calculate Backup Withholding

The backup withholding rate is a flat 24% applied to the gross amount of each reportable payment. There are no deductions, exemptions, or graduated rates -- it is a straightforward percentage calculation.

Key points about the calculation:

• The 24% applies to each payment individually, not to a cumulative total
• Withholding applies from the first dollar -- there is no minimum payment threshold
• The rate has been 24% since 2018 and is set by statute; it does not change annually with tax brackets
• You must withhold from each payment made after the trigger date, including payments for work completed before the trigger

Your Liability as a Payer

This is the most critical concept in backup withholding: you owe the IRS the 24% whether or not you actually withhold it from the payee's payment. If backup withholding is triggered and you continue paying the vendor the full gross amount without deducting 24%, you are still liable to the IRS for the withholding amount.

In practical terms, this means a failure to withhold results in paying the IRS 24% of the payment amount out of your own funds, on top of the full payment you already made to the vendor. The IRS treats this as a trust fund obligation -- the money belongs to the government from the moment the trigger event occurs.

This is why understanding what happens when a TIN doesn't match is so important. A TIN mismatch that seems like a minor data error can quickly become a significant financial liability.

How to Report Backup Withholding

Form 945: Annual Return of Withheld Federal Income Tax

Backup withholding is reported and remitted to the IRS using Form 945 (Annual Return of Withheld Federal Income Tax). This is a separate filing from your employment tax returns (Forms 941/944). Key details:

• Filing deadline: January 31 of the year following the calendar year in which you withheld
• Deposit requirements: You must deposit withheld amounts according to the IRS semi-weekly or monthly deposit schedule, using EFTPS (Electronic Federal Tax Payment System)
• Penalties for late deposits: Late deposit penalties range from 2% to 15% of the amount, depending on how late the deposit is

Reporting to the Payee

You must report backup withholding on the payee's 1099 form. Box 4 on most 1099 forms (including 1099-NEC and 1099-MISC) is designated for "Federal income tax withheld." Enter the total amount withheld during the calendar year. The payee uses this information to claim a credit on their income tax return.

How to Stop Backup Withholding

Backup withholding is not permanent. Once the underlying issue is resolved, you can (and must) stop withholding. The process for stopping withholding depends on what triggered it:

After a First B-Notice

If backup withholding started because a payee did not respond to a First B-Notice, you can stop withholding when:

1. The payee provides a completed, signed W-9 with their correct name and TIN
2. You verify the name/TIN combination using IRS TIN matching
3. The verification confirms the TIN is correct

Once you have a verified W-9, stop withholding beginning with the first payment made more than 30 days after you receive the certified TIN.

After a Second B-Notice

If backup withholding started because of a Second B-Notice, the requirements are stricter. You can only stop withholding when:

1. The payee provides written validation from the IRS or SSA confirming their TIN
2. You verify the information independently

A W-9 alone is not sufficient after a Second B-Notice. The payee must have contacted the IRS or SSA directly and obtained validation.

After an IRS Direct Notification

If the IRS sent you a direct notification to begin withholding, you can only stop when the IRS sends you a follow-up notification authorizing you to stop. Do not stop withholding based on information from the payee alone.

Backup Withholding and Your Vendor Relationships

Beyond the financial mechanics, backup withholding creates real problems for vendor relationships. When you suddenly deduct 24% from a vendor's payment with no prior warning, the vendor sees a significantly smaller check and wants to know why. This leads to:

• Payment disputes -- Vendors may dispute invoices, delay services, or threaten to terminate the relationship.
• Cash flow problems for the vendor -- The 24% withholding reduces the vendor's available cash. While the vendor can claim the withholding as a credit on their tax return, they will not see that money until they file.
• Administrative burden -- Your AP team must handle vendor inquiries, explain the withholding, and manage the additional paperwork for Form 945 and corrected 1099s.

The best way to protect vendor relationships is to prevent backup withholding from being triggered in the first place. A robust vendor compliance program that includes TIN verification at every stage catches problems before they escalate to withholding.

Form 945 Filing: A Closer Look

If you withhold any backup withholding during the year, you must file Form 945. Here is what you need to know:

The Connection Between B-Notices and Backup Withholding

The B-Notice process and backup withholding are tightly linked. Here is the typical sequence:

1. The IRS sends you a CP2100 notice identifying payees with mismatched TINs.
2. You send a First B-Notice to each affected payee within 15 business days.
3. If a payee does not respond within 30 days, backup withholding begins.
4. If the same payee appears on a subsequent CP2100 within three years, you send a Second B-Notice and backup withholding begins immediately.
5. Backup withholding continues until the payee resolves the issue (W-9 for First B-Notice, IRS/SSA validation for Second B-Notice).

At every step, the IRS expects you to document your actions. This documentation is essential for the reasonable cause defense if penalties are assessed.

Penalties for Failing to Withhold

If you fail to withhold when required, the IRS can assess:

• The withholding amount itself -- You owe the 24% whether or not you deducted it from the payee's payment.
• Penalties for incorrect information returns -- Filing a 1099 without reporting the correct withholding amount in Box 4 is an incorrect return, subject to per-return penalties.
• Trust fund recovery penalties -- In severe cases, the IRS may assess trust fund recovery penalties against responsible individuals within the organization.
• Interest -- Interest accrues on unpaid withholding amounts from the date they should have been deposited.

How Proactive TIN Matching Prevents Backup Withholding

Backup withholding is always the result of an earlier failure: a TIN that did not match the IRS records. If every TIN on your 1099 filings matches before you file, the IRS has no mismatches to flag, no CP2100 notices to send, no B-Notices for you to issue, and no backup withholding to trigger.

TINCorrect makes this level of prevention practical for organizations of any size:

By integrating TIN verification into your vendor onboarding process and running bulk verification before each filing season, you address mismatches at the point of origin. Organizations that adopt this approach typically eliminate backup withholding obligations entirely, along with the administrative burden and vendor relationship strain that comes with them.

Review our 1099 compliance checklist to see where TIN verification fits into your year-end workflow, or explore AP TIN verification to understand how accounts payable teams integrate verification into daily operations.

Frequently Asked Questions

Author

Ken Ham

Founder at TINCorrect

Passionate about making tax identity verification simple so businesses can focus on what matters.