Sales document basics

Invoice vs Quote / Estimate: What's the difference?

A quote sets price expectations before any work happens. An invoice is the bill you send after the work is done. Same client, two different documents — issued at opposite ends of the project.

TL;DR

A quote is a non-binding price proposal sent before work begins so the client can decide whether to hire you. An invoice is the legally binding bill sent after delivery so the client pays you.

Quote / Estimate

Sets the price — issued before work begins

A quote (or estimate) is a written offer to perform work for a stated price. It describes the scope, the price, and how long the offer is valid. A quote is typically not binding until the client accepts it, at which point it becomes a contract.

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Invoice

Collects the price — issued after work is delivered

An invoice is a commercial document the seller issues after work or goods have been delivered, itemizing what was provided, the agreed price, taxes, and the payment deadline. It is the legal trigger for accounts receivable.

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Invoice vs Quote at a glance

Attribute	Quote / Estimate	Invoice
Purpose	Bill for completed work	Propose a price for future work
Issued when?	After delivery	Before work begins
Legally binding?	Yes — creates a debt	No, until the client accepts it
Price changes?	Final unless re-issued	Can change until accepted
Required fields	Invoice number, date, due date, line items, tax, amount due	Quote number, valid-until date, scope, line items, total
Tax treatment	Triggers VAT/sales tax obligations	No tax obligation until invoiced
Used in accounting	Recorded as receivable / payable	Not recorded — informational only
Typical example	INV-2026-0042 sent at project end	EST-2026-0007 sent before kickoff

When to use which

Send a quote when…

You need the client to approve scope and price before you start working.

Custom project work where price depends on scope
Construction, design, or consulting engagements
Tender / RFP responses
Any client who asks 'how much will this cost?'

Send an invoice when…

Work is delivered (or a milestone is reached) and you want to be paid.

Project completion or milestone delivery
Recurring monthly retainer billing
Time & materials billing for hours worked
Any moment a payable amount becomes due

Frequently asked questions

Can a quote become an invoice?

Yes. The standard workflow is: send a quote → client accepts it → deliver the work → convert the quote into an invoice with the same line items. Most invoicing software has a one-click 'convert quote to invoice' action.

What's the difference between a quote and an estimate?

In most jurisdictions a quote is a fixed price the seller commits to, while an estimate is a best-guess that may change. In casual usage the words are interchangeable, but in trades like construction the distinction matters legally.

Is a quote a contract?

Not by itself. A quote becomes a contract once the client accepts it (in writing, by email, or by signing). Until then either party can walk away. Always include a 'valid until' date so old quotes don't bind you.

Do I have to honor a quote forever?

No. Set an expiry date — typically 14 to 30 days — so you're not locked into a price after costs have changed. Once expired, the quote is void and you can re-issue it at a new price.

Related comparisons

Invoice vs Receipt: What's the difference?

An invoice asks for payment; a receipt confirms it.

Pro Forma Invoice vs Commercial Invoice

Pro forma is a preview; commercial is the customs-grade real thing.

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