What is vendor onboarding in accounts payable?

Start with a single intake point - a form, not an email thread - that captures legal name, tax classification, W-9/W-8, remit-to address, banking details, and the business justification. Define what's required before activation (tax form, verified banking, duplicate check), assign one owner for validation, and require an approval separate from the requester. Then make "no complete onboarding, no payment" the policy. Emailing a W-9 request and hoping is not a process; it's a fraud surface.

Self-service through a secure portal is better for accuracy and liability: the vendor enters their own tax and banking data, which removes AP keying errors and creates an attributable record of who supplied what. AP-managed onboarding still makes sense for low-volume vendor files or vendors who can't or won't use a portal. Most teams land on portal-first with an AP-managed exception path.

Five steps with clear owners: (1) requester submits the intake request with business context; (2) vendor completes a self-service form - tax docs, banking, contacts; (3) AP or vendor management validates - duplicate check, TIN check, bank verification; (4) an approver who isn't the requester or the validator activates the vendor; (5) the record syncs to the ERP. Each handoff should be visible in one system, not reconstructed from email.

They're the same activity viewed from different seats - "supplier onboarding" is the procurement/supply-chain term, "vendor onboarding" the AP/finance term. Procurement-led versions add sourcing and qualification steps; the AP core (tax, banking, compliance, approval) is identical.

The requester initiates and provides context; AP (or a vendor management function) owns validation and data quality, because AP bears the payment and 1099 consequences. Procurement owns it where a formal sourcing program exists - but one function must be accountable for the record.

Park the invoice in a pending state, send the vendor your onboarding form (portal link or W-9 request) using contact details from an independent source - not just the invoice - and don't release payment until tax and banking data are validated.

Onboard them immediately and retroactively: W-9 before first payment (you have maximum leverage while money is owed), banking verification, and a note to the hiring manager that future engagements require onboarding first. No payment until the record is complete.

Before, ideally - issuing a PO to an unvetted vendor commits spend to an entity you haven't verified. If speed requires it, allow PO issuance against a "pending" vendor but block payment until onboarding completes.

At minimum: validation evidence (tax form, duplicate check, bank verification) plus sign-off from someone who didn't request or create the record. Higher-risk vendors - high spend, international, banking changes - warrant a second approver.

Cover identity (legal name, DBA, EIN/SSN, address), tax (W-9/W-8, 1099 determination), payment (banking, remit-to, terms, currency), compliance (COI, licenses, certifications by industry), and governance (requester, approver, date). Industry add-ons: lien waivers and licenses for construction, exclusion checks for healthcare.

Email is universal but insecure, unstructured, and unauditable. A standalone portal is secure but creates another silo. Onboarding inside the AP platform combines portal security with direct connection to invoices, payments, and the ERP record - one less reconciliation.

Self-service collection with customizable forms, secure document handling, duplicate and TIN checking, bank-detail verification workflow, approval routing, ERP sync, and a complete audit trail. If it can't block payment for incomplete vendors, it's a form builder, not a control.

A lightweight one-time-vendor path is acceptable for genuinely single payments below a defined threshold - but still collect a W-9 if the payment is reportable, and review one-time vendor usage monthly, because it's a classic fraud and policy-bypass channel.

Individuals/sole proprietors need SSN/EIN handling care and almost always 1099 tracking; corporations are usually 1099-exempt (attorneys and medical excepted) but warrant entity verification; government entities skip 1099 logic but may have specific remittance requirements.

An expedited lane, not a bypass: same required data, compressed timeline, verbal-then-documented approvals, and a flag that triggers full review within a set window. Emergencies justify speed, never skipped verification of banking details.

Centralize the standards and the validation (one duplicate check, one tax process, one banking verification protocol); let entities initiate requests. Distributed creation with no central control is how duplicate and fraudulent vendors enter the file.

Stampli supports vendor onboarding by connecting supplier information, payment details, required documentation, vendor communication, and ERP vendor context to AP and payment workflows. Vendor self-service can reduce manual collection work, while finance teams retain review and control over vendor records before invoices or payments move forward. The ERP remains the system of record, and Stampli keeps the onboarding and payment-readiness context visible inside the P2P workflow.