What is the difference between an estimate and an invoice?

An estimate is a quote you send for approval; an invoice is the request for payment. Converting an estimate carries its line items, taxes, customer and custom fields across in one step, so nothing is retyped, and the two records stay linked to each other afterwards. The estimate does not have to be accepted first — an active one converts too — but a cancelled or expired one will not.

Estimates never move stock, even when the items on them are linked to stock. Stock moves when the invoice they became reaches the stage that consumes it.

Where a customer has portal access, they can accept or decline an estimate themselves and the decision is recorded against it. On a plain share link they can read and download it but not approve it.

The new invoice takes its document settings — notes, terms, footer, signature block — from your organization defaults rather than from the estimate. Attachments and the message thread can optionally be carried across as well.