Invoice vs Quote: What's the Difference?

The core difference

A quote is sent before any work begins. It tells your client what you expect to charge, so they can decide whether to move forward. An invoice is sent after (or during) the work, requesting actual payment for what was delivered. The two documents look similar — business details, line items, a total — but they serve opposite moments in the same relationship: one proposes a price, the other collects it. Both can be made for free: the quote generator before the job, the invoice generator after.

When to send a quote

Send a quote whenever a client asks "how much will this cost?" before committing. A good quote includes a scope of work, your price (fixed or estimated), and how long the quote is valid — prices can change, and an open-ended quote can come back to bite you months later. If the scope isn't clear enough to commit to a fixed price yet, send an estimate instead: an approximate figure that can move once the full job is known.

When to send an invoice

Send an invoice once the work is complete, or at agreed milestones for larger projects. Unlike a quote, an invoice is a request for payment now, with a due date attached.

Is a quote legally binding?

In the UK, yes — once your client accepts it, a quote becomes a binding agreement at that price, and you generally can't charge more afterward without a valid reason like a change in scope. For work done for consumers, the Consumer Rights Act 2015 backs this up: anything you say or write about the service that the customer takes into account when deciding to hire you is treated as a term of the contract (section 50). And if no price was fixed at all, the customer only has to pay "a reasonable price for the service, and no more" (section 51) — which may be less than the number you had in mind.

In the US, there's no equivalent federal statute, but a written, accepted quote still functions as a contract under ordinary offer-and-acceptance principles. The FTC's advice to homeowners hiring contractors doubles as a checklist for any quote you send: "a written estimate should include a description of the work to be done, materials, completion date, and the price" (FTC — How To Avoid a Home Improvement Scam). The quote generator page covers how quotes and estimates differ under both systems.

Can a quote become an invoice?

Yes, and it's common practice. Once a client accepts your quote and the work is done, you convert it into an invoice with the same line items, a payment due date, and your payment details added. Referencing the original quote number on the invoice makes it easy for both sides to confirm the final bill matches what was agreed.

What if the price changes after the quote?

If the scope changes mid-project, it's worth sending an updated quote or getting written confirmation before invoicing a different amount. Invoicing significantly more than a client quoted, without warning, is one of the fastest ways to create a payment dispute.

Ready to send one? Create a free quote, create a free invoice, or see how to make an invoice once your quote is accepted.