Deze gids is nog niet vertaald in jouw taal — je ziet de Engelse versie.
For anything beyond a simple, immediate sale, a job doesn't go straight from "let's talk" to "paid." It moves through a handful of distinct stages, each with its own document. Knowing the sequence — and using the right document at each step — keeps both you and the client clear on where things stand.
1. Estimate: rough numbers, early conversation
An estimate is a ballpark figure given before all the details are settled — useful when scope might still shift, or when the client is comparing options and just needs a workable number to plan around. It's explicitly not a firm commitment on either side.
2. Quote: a firm, specific offer
Once scope is clear, a quote replaces the estimate with a specific, priced proposal the client can actually accept. Unlike an estimate, a quote is usually treated as binding once accepted — so only send one when you're confident in the number.
3. Purchase order (client-issued, sometimes)
For business clients with formal procurement, the client may issue you a purchase order once they accept your quote — their own internal authorization to proceed and pay. Not every client does this, but when they do, it's worth referencing their PO number on your invoice.
4. Work begins — and, for larger jobs, progress billing
For short engagements, work simply starts. For longer projects, it's common to invoice at milestones rather than waiting until everything is finished — reducing how much of your own cash is tied up in an unfinished job. Each milestone gets its own invoice.
5. Invoice: the request for payment
Once work (or a milestone) is complete, the invoice goes out — the formal request for payment, referencing the accepted quote and any PO number. This is the document that starts the payment clock, using whatever terms you agreed on (see setting payment terms).
6. Payment and receipt
Once the client pays, a receipt confirms it — closing the loop and giving the client something for their own records.
7. If something needs correcting
If an invoice was overstated, or goods were returned, a credit note adjusts the balance without editing a document that's already been sent and recorded.
Why the sequence matters
Skipping steps — jumping straight to an invoice without an agreed quote, for instance — is where most billing disputes start. Each document in the sequence exists to remove one specific kind of ambiguity: what it costs, what was agreed, what's owed, and what's been paid. Used in order, they leave very little room for a client to be surprised by anything on their invoice.