An estimate or quote is a price before the work
An estimate tells the client what you expect the job to cost. A quote is usually a firmer, fixed price. Local custom and law differ on how binding each one is, so say clearly in writing which one you mean and how long it is valid.
An invoice is a request for payment after (or during) the work
An invoice asks for money that is owed. It has a number, a date, what was delivered, the amount, and how to pay. It is the document your bookkeeping and your client’s accounts both rely on.
When to send which
• Client asks “how much?”: send an estimate or quote
• Client says yes: ask for a deposit if the job is large
• Work is done or a stage is complete: send the invoice
• Client has not paid by the due date: send a polite reminder
Turning an estimate into an invoice
Re-typing an accepted estimate as an invoice invites mistakes. In tracks-it PDF a client can accept an estimate and sign it with a finger on their phone, and you can convert it to an invoice in one step. A deposit paid on the estimate is carried over, so the invoice shows what is still owed.
More guides
How to write an invoice that gets paidHow small businesses can get paid fasterCreate an invoice by voice from your phoneGeneral information, not legal or tax advice. Rules differ by country.