Quotation vs Invoice vs Proforma — Which Document Do You Need?

"Quote", "invoice" and "proforma" get used interchangeably by clients — but they are three different promises. Mix them up and you either give away your pricing freedom or send a document that legally asks for money before the work exists. Here is the clean version.

Quotation — a price offer that expires

A quotation says: for this scope, I will charge this much, and the offer stands until this date. Nobody owes you anything yet — which is exactly why two lines matter most: the scope in words (what is included, and what extras cost) and the validity date. Material prices and exchange rates move; a quote with no expiry is a price-lock you handed out for free. Seven to fifteen days is a healthy validity.

Invoice — the request for payment

Once the work is delivered (or per agreed milestones), the invoice states what is owed and by when, under a unique number. Unlike a quote, an invoice normally reflects completed or contractually due work. Send it early and you train clients to argue with your dates; send it late and you queue behind everyone else's payments.

Proforma — the paperwork version of a quote

A proforma invoice is a quotation wearing an invoice's clothes. It exists so the buyer can arrange an advance, an import permit or a letter of credit. It should never enter either side's books as a debt — which is why the real invoice stays separate and properly numbered.

The lifecycle that keeps you paid

Quote → accepted → invoice → part-payments → statement. Every arrow is where small businesses leak money: an accepted quote that never became an invoice (work given away), an invoice that never recorded the payment already made (an embarrassing double-bill), no statement at year end (forgetting who owes what). The fix is boring and it works: every quote converts into an invoice that references its quote number, and every payment posts against the invoice and lands in one running ledger per party.

Stop retyping between the two documents

Retyping is where mistakes live — scope copied from a three-week-old quote, totals added differently, a payment that exists on the books but not on the bill. Use one template per client you edit carefully, or a tool that converts the quote into an invoice in one click so the client, currency, items and numbers carry over untouched. When the invoice prints "Against quote QT-0007", nobody re-argues the price.

Frequently asked questions

Is a quotation legally binding?

Usually a quote is an offer that becomes binding when the client accepts it — which is why the validity window and the scope wording are what you are actually committing to. A quote with vague scope binds you to vague work, and that is how projects die. This is general guidance, not legal advice.

Can I change or cancel an invoice?

Do not edit and resend under the same number — the old PDF is already in someone's inbox, and two versions of one number create disputes. Issue a corrected invoice with a new number referencing the old one, or a credit note if only part was wrong. Clean numbering is your defence.

Do quotes and invoices share a numbering series?

Either way is fine as long as each series is unique and ordered. Separate prefixes (QT-… and INV-…) are easier on the eye when both documents circulate together.

Related: Invoice checklist  ·  Tracking client balances  ·  Deposits and milestones

General guidance only — not legal, tax or accounting advice. Local rules on tax fields, numbering and late fees vary; confirm specifics for your business with a professional.