← All posts · 2026-07-24

The four-document vendor onboarding checklist

Vendor onboarding is four documents. Collect them before the first day of work and almost every downstream mess gets smaller. Chase them after the work starts and you have lost your leverage.

1. W-9

You need it to issue a 1099, and January is the worst possible time to discover you never got one. Collect it first because it is the document vendors resist least; it sets the precedent that paperwork precedes work.

2. Certificate of Insurance

The document that protects you when their work goes wrong. Capture the expiration date and policy number as data, not just as a PDF, because the expiration date is the part you have to act on later. If you require additional insured status, check for it now, not during a claim.

3. Banking info

Collect payment details once, through a channel you control. Ad hoc banking updates over email are how payment fraud happens; a structured intake with a known link is dramatically harder to spoof than a reply-all thread.

4. Signed NDA or subcontractor agreement

Whatever your standard terms are, signed before access to plans, pricing, or the site. Unsigned agreements have a way of staying unsigned exactly until the dispute that needed them.

The order matters less than the gate

The rule that makes this work is simple: incomplete vendors do not start work. One glance at your vendor list should show who is cleared, who is missing documents, and whose insurance is about to lapse. If seeing that takes more than a glance, the process will decay the first busy month.