Is a quotation legally binding like an invoice?

A quotation is an offer, not a demand for payment — it becomes binding only once the client accepts it, usually by confirming in writing or paying a deposit. An invoice is a formal request for payment for work already agreed or delivered, and is used as a legal/accounting record.

Can I turn a quotation into an invoice?

Yes — once a client accepts your quotation, convert it into an invoice by keeping the same line items and client details, changing the document title, and adding payment status and bank details. Tools like ProQuote do this conversion in one click.

Invoice vs Quotation: What's the Difference?

"Should I send them a quotation or an invoice?" It's one of the most common questions from people new to running a business — and getting it backwards can confuse clients or, worse, make you look like you're demanding payment for work they haven't agreed to yet.

The short version: a quotation comes first and proposes a price. An invoice comes after and demands payment. Here's exactly where the line is, and how to move from one to the other.

The Core Difference

	Quotation	Invoice
Sent	Before work begins	After work is agreed or delivered
Purpose	Propose a price and scope	Request payment
Legal weight	An offer — not binding until accepted	A formal payment demand / accounting record
Editable?	Yes, freely — it's a proposal	Should not be edited once issued (create a credit note instead)
Expires?	Yes — typically 15–30 days	No — but has a payment due date
Contains	Price, scope, validity date	+ payment status, bank/payment details, due date

A Simple Way to Remember It

A quotation asks "would you like to proceed at this price?" An invoice says "you agreed to proceed — please pay."

If the client hasn't said yes yet, you need a quotation. If they've already agreed (or you've already delivered), you need an invoice.

When to Send a Quotation

A new client asks "how much would this cost?"
You're bidding for a project against other providers
The scope of work might still change before it's confirmed
You want the client to formally agree to a price before you start

When to Send an Invoice

The client has confirmed they want to proceed
Work is complete, or a milestone/deposit is due
You need a formal record for your own accounting and tax filing
You're chasing payment for goods or services already delivered

What Happens if You Get It Backwards?

Sending an invoice instead of a quotation to a client who hasn't agreed yet can feel presumptuous or confusing — you're demanding payment for something they haven't approved. Sending a quotation instead of an invoice after work is done sends the wrong signal too: it implies the price is still negotiable when it shouldn't be.

Some countries also treat the two differently for tax purposes — an invoice is typically what triggers VAT/GST reporting obligations, while a quotation does not, since no sale has occurred yet.

Converting a Quotation Into an Invoice

Once a client accepts your quotation, you don't need to start over. Carry across:

Client details and line items — unchanged
Change the document title from "Quotation" to "Invoice"
Assign a new invoice number (keep quotation and invoice numbering separate, e.g. PQ- vs INV-)
Add payment status (Unpaid), due date, and bank/payment details
Remove the "valid until" field — invoices don't expire, they fall overdue instead

ProQuote does this conversion automatically — open any saved quotation, choose "Convert to Invoice" from the menu, and everything above happens in one tap.

Create Both, in One Place

Quotation now, invoice later — same tool, one click to convert.

Create a Quotation →

Key Takeaways

A quotation is a price proposal sent before work starts; an invoice is a payment demand sent after
Quotations expire and can be freely edited; invoices shouldn't be edited once issued
Getting the order backwards confuses clients and can complicate your own tax records
ProQuote converts an accepted quotation into an invoice automatically, keeping all the details