Going from quote to invoice is the most repeated task in small business admin, and the one most often done by retyping. It should not be.
Reopen the quote, do not retype it
Every sheet on this site saves to a file you keep. Reopen the saved quote, and the customer, the line items, the prices and your own details are already there.
What follows is a short list of changes rather than a fresh document.
The seven changes
- The document type. Quote becomes Invoice.
- The number. A new number from your invoice sequence, not the quote’s.
- The date. Today, not the quote date.
- The due date. A quote has a validity period; an invoice has a due date.
- The reference. Add “Per quote QTE-0044” so both documents point at each other.
- The line items. Only if the work changed. More on that below.
- The wording. Anything conditional (“this price holds until”) comes out.
Save the result under its own name. You now have both files, which is what you want when a question arrives in three months.
Reference the quote by number
One line, and it removes most of the follow-up email:
Invoice INV-0087
Per quote QTE-0044, accepted 2 August 2026The customer’s accounts team can now match your invoice against the approval they hold. Without it, someone has to go looking, and looking takes days.
Numbering your documents covers keeping the two sequences separate and both traceable.
When the work grew
This is the part that goes wrong. If the invoice is larger than the quote and nothing explains why, expect a query.
Keep the quoted items as quoted, then add the extras as their own lines with their own explanation:
Description Amount
Bathroom refit, per quote QTE-0044 420,000
Replace corroded supply pipe, approved 14 Aug 38,000
Total 458,000The customer can see what they agreed and what they added. Approving extra work covers getting that approval on paper before the invoice, which is when it is easy.
When the work shrank
Bill what you did. Do not invoice the quoted figure and quietly plan to sort it out later, because later is a credit note and a conversation.
If the customer paid a deposit against the larger figure, show the deduction on the invoice. Deposits and staged payments covers the arithmetic.
If it was an estimate, not a quote
Different documents with different obligations. A quote is a fixed price; an estimate is a considered guess. Invoicing an estimate at a different figure is normal, and invoicing a quote at a different figure needs agreement.
Quote or estimate covers which you sent.
The proforma case
If you sent a proforma invoice to get payment released or goods cleared, the real invoice still has to follow. A proforma is not a tax document and the customer’s accounts cannot close against it.
What is a proforma invoice covers the difference.
Keep both documents, forever
The saved quote is not a draft that the invoice replaces. It is the evidence of what was agreed, and it is the first thing you will want if the invoice is ever questioned.
Save both, named so they sit next to each other:
qte-0044-acme-2026-07-18.json
inv-0087-acme-2026-08-02.jsonOrganising your invoice files covers the folder they live in.
Do not reuse the quote’s number
Tempting, because it feels like the same transaction. It is not, and the two documents are counted separately by anyone reconciling them.
Each sequence rises on its own. Numbering your documents covers keeping them apart without keeping two lists in your head.
What to do with a quote that was never accepted
Nothing, and that is the point. An unaccepted quote does not become an invoice because the deadline passed, and invoicing against one is a fast way to lose a customer who thought they had declined.
If a quote has expired and the customer resurfaces, requote. Prices move, and how long a quote lasts covers stating the validity so this is a non-conversation.
Part-completed work
Where a quoted job is stopped partway, do not invoice the quoted figure and do not guess. Invoice the work actually done, itemised against the quote so the customer can see which parts were completed.
Description Amount
Per quote QTE-0044:
Strip out and disposal, complete 68,000
First fix, complete 94,000
Second fix, not started 0
Total 162,000Showing the zero is worth more than omitting the line. It tells the reader that nothing was overlooked.
Two customers, one quote
Occasionally a quote is accepted by someone other than the person who will pay: a tenant against a landlord, a site manager against a head office, a customer against an insurer.
Invoice the payer, name the approver. The To field carries whoever settles the bill; a reference line carries who agreed it.
To Riverside Property Ltd
Reference Per quote QTE-0044, approved on site by J. Mwangi, 18 JulyWithout that second name, the payer has an invoice they did not agree to, and it stops in their approvals queue.
Make it a habit
Reopen, change seven fields, save, print. How to make an invoice covers the sheet itself, and how to write a quote covers the document you started from.
Start at the quote maker, and the invoice at the end of the job costs you two minutes.