A quote is a firm offer. If the customer accepts it, you have agreed to do the work for that money. An estimate is your considered opinion of what the work will cost, given what you know now.
Customers frequently use the words interchangeably. You should not.
Send a quote when
The scope is settled and you can see the whole job. A fixed deliverable, a known quantity, a site you have visited. You are confident enough in the number to be held to it.
Put an expiry date on it. Materials move, and a quote with no expiry is an open offer you may be held to months later.
Send an estimate when
The scope is not settled, or the work depends on what you find. Repairs, surveys, anything behind a wall. The honest answer is a range and the reasons it might move.
An estimate should say what it assumes. “Assumes existing wiring is serviceable” is the sentence that saves an argument later.
Writing an estimate that does not trap you
Three things make the difference:
- State the assumptions. What you have priced for, and what you have not.
- State the tolerance. Many trades write “the final figure will not exceed this estimate by more than 10% without your approval”. That is a promise the customer can rely on and you can live with.
- State what triggers a new number. If the job changes, say who decides and how the customer will be told.
The trap in the middle
The dangerous document is the one labelled “estimate” that reads like a quote: a single confident figure, no assumptions, no tolerance. Customers read the number, not the heading. If you cannot commit to the figure, the document has to show why.
After it is accepted
Neither a quote nor an estimate asks for money. When the work is done, bill the real numbers on an invoice and reference the quote number on it so both sides can match the two.