---
title: "W-9 form: definition | Rex glossary"
description: "A US IRS form a supplier gives its customers to confirm its legal name and taxpayer identification number. Many AP teams won't pay without one."
canonical: https://www.rex.inc/glossary/w-9-form
---

# W-9 form

A US IRS form a supplier gives its customers to confirm its legal name and taxpayer identification number. Many AP teams won't pay without one.

Buyers use the W-9 to collect the details they need for 1099 reporting and backup withholding. Requests arrive at onboarding and again whenever a customer refreshes its vendor records.

It's one of the most common routine requests in an AR inbox, and quick to resolve when a current signed copy is on hand.

## Related terms

- [Supplier onboarding The paperwork a new customer needs before it will pay you: vendor forms, tax documents, bank details and portal registration.](https://www.rex.inc/glossary/supplier-onboarding)
- [AR inbox The shared mailbox where customers send remittances, invoice requests, disputes and questions to a company's accounts receivable team.](https://www.rex.inc/glossary/ar-inbox)
- [Customer master data The core record for each customer in the ERP: legal entity, billing and remit-to addresses, contacts, payment terms, tax details and credit limit.](https://www.rex.inc/glossary/customer-master-data)

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