Vendor payment compliance is the intersection of accounts payable operations and tax law. Finance teams who get this wrong face year-end scrambles to collect missing W-9s, backup withholding obligations they were not tracking, and 1099 penalties that are entirely avoidable.
This guide covers the compliance obligations that finance teams own and the controls that prevent the most common problems.
The W-9 Gate
An important control is obtaining the appropriate tax documentation before the first reportable payment when practicable. A payment hold must still align with contracts, prompt-payment rules, and the IRS backup-withholding framework.
This sounds obvious. It is not universally practiced. The typical failure pattern: a vendor is engaged, starts work, submits an invoice. The invoice is approved and goes to AP. AP pays it. Someone remembers to collect the W-9 later. Or they do not.
By the time January arrives and 1099-NECs need to go out, the vendor may be unresponsive, may have changed their business information, or may have been a sole proprietor who used a personal SSN that they are now reluctant to provide.
The fix: Define who collects the tax form, when the vendor record may be created, when backup withholding applies, and how AP handles a valid invoice if documentation is missing. Do not substitute an internal hold for required backup withholding.
Backup Withholding
Backup withholding is a 24% withholding obligation on payments to vendors when:
- The vendor fails to provide a TIN when required
- The IRS notifies you (via a B Notice) that the TIN the vendor provided does not match their records
- The vendor fails to certify their TIN exemption from backup withholding
The backup withholding is remitted to the IRS using Form 945. It is reconciled against the vendor's annual tax return, so it is not a permanent cost to the vendor, but it is a significant administrative burden and a source of vendor relationship friction.
The B Notice process: Publication 1281 instructs payers to compare the IRS listing with their records and, when required, send the appropriate notice within 15 business days. Backup-withholding start and stop timing depends on whether the TIN is missing, obviously incorrect, or mismatched and on the first- or second-notice procedure. A second listing within three calendar years generally calls for the Second B Notice and specified SSA or IRS validation rather than another W-9. Follow the current publication instead of reducing the process to one deadline.
The volume of B Notices you receive is directly correlated with how rigorously you verified W-9 information at collection. Companies that collect W-9s casually receive more B Notices.
The 2026 Threshold and What It Covers
For payments made in 2026, the Form 1099-NEC threshold for nonemployee compensation is $2,000; for later years it is indexed for inflation. Other forms and payment categories can use different thresholds. See our contractor-onboarding guide.
It applies per calendar year, per payee. Once aggregate reportable payments reach the applicable threshold, report the annual amount as the form instructions require.
Payment type matters. Form 1099-NEC generally covers nonemployee compensation for services, including parts and materials tied to the service. Other payments may belong on another form or be excluded. Use the current instructions.
Corporate exemptions have exceptions. Current IRS instructions treat legal and medical or health-care payments specially and distinguish attorneys' fees from gross proceeds. Do not rely on entity type alone.
It does not apply to payroll. Employee wages are reported on W-2s. This guide covers non-employee payments only.
Payment Hold Policies for Missing Documentation
Finance teams should have a written policy specifying when payments are placed on hold pending compliance documentation. Recommended policy elements:
W-9 or TIN missing: Apply the current IRS solicitation and backup-withholding rules, and coordinate any payment hold with the contract and applicable payment law.
Backup withholding triggered: Withhold 24% from reportable payments, make deposits under the applicable monthly, semiweekly, or next-day rules, report annual nonpayroll withholding on Form 945, and document it in the payment record.
Expired insurance for on-site vendors: Coordinate with operations for work hold decisions; finance holds payment for any invoices covering work performed during the lapse period until the compliance question is resolved.
Tax exemption certificate expired: Hold tax-exempt treatment; charge sales tax on invoices until a valid certificate is on file.
Year-End 1099 Preparation
Start year-end review early enough to identify payees approaching the current threshold, solicit missing forms, resolve exceptions, and complete filing. Eligible payers and authorized agents may apply to use the IRS TIN Matching Program before filing.
The IRS TIN Matching Program is a pre-filing service for eligible payers and authorized agents. It can help identify mismatches, but it does not guarantee that a return is correct or eliminate all notices.
Building Compliance Into AP Processes
The compliance controls that matter most in vendor payment compliance are operational controls, not financial controls. They happen at vendor onboarding (W-9 collection), at payment setup (W-9 verification), and at the point of processing (hold policies for missing documentation).
Finance teams that own payment compliance but do not own vendor onboarding need a formal handoff: compliance documents collected at onboarding, verified information passed to AP, and a clear status indicator in the payment system showing which vendors have complete documentation on file.
A vendor compliance platform creates this handoff automatically: the payment clearance flag in your AP system is driven by the document status in the compliance system, with no manual coordination required.