The four documents side by side
- Quote — fixed price offer, pre-sale, not an accounting document
- Estimate — approximate quote, signals the price may move
- Proforma invoice — invoice-shaped quote, used to arrange payment/import
- Invoice — the accounting document, issued on delivery, creates tax liability
Which one at which stage
Scoping? Send an estimate. Client ready to commit? Send a quote with a validity date. Buyer's finance needs paperwork to release a deposit? Send a proforma. Work delivered? Send the final invoice for the accepted amounts — same lines as the quote, real sequence number.
Keeping the numbers straight
Give each document type its own sequence: Q- for quotes, PI- for proformas, plain or INV- for invoices, CN- for credit notes. A quote that becomes a sale keeps its quote number in the notes; the invoice gets the next real invoice number.
Frequently Asked Questions
Is a quote legally binding?
It can be: within its validity period, a quote is an offer the client can accept, and acceptance forms a contract. Expire quotes explicitly and state assumptions in the notes.
Can I skip the quote and send a proforma?
For simple deals, yes — a proforma is essentially a quote in invoice clothing. But keep them separate for formal sales: procurement teams route quotes through vendor onboarding and proformas through payments.
Must the invoice match the quote?
Where work was delivered as quoted, yes — matching line for line gets invoices approved fastest. Changes get documented: new line, or a credit note against a wrongly invoiced amount.