Estimate, quote, invoice: what the difference actually is
These three words get used as though they mean the same thing. They do not, and the difference is the difference between being able to charge for extra work and having to absorb it.
An estimate is a considered guess
An estimate says: based on what I can see, this is what I expect the job to cost. It is given before anyone has opened a wall. If the job turns out to be larger — the joists are rotten, the run is twice as long as it looked — the figure can change, provided you say so at the time and the customer agrees.
That flexibility is the point of an estimate, and it is also why an estimate needs to say clearly what it is. Write Estimate at the top. Say what it covers and, more usefully, what it does not.
A quote is a promise
A quote is a fixed price. Once the customer accepts it, that is what the job costs, whatever it turns out to involve. In many places an accepted quote is a contract, and the person who wrote it carries the risk of having read the job wrong.
That is not a reason to avoid quoting. Customers prefer a fixed price and will often pay more for one, because you have taken the uncertainty off them. It is a reason to quote only when you can see the whole job, and to write down the assumptions the price depends on.
An invoice is a demand for payment
An invoice comes after the work, or after an agreed stage of it. It is an accounting document, not a proposal: it carries a number, a date, what is owed, and by when. Most tax authorities have rules about what an invoice must show and how long you must keep it — an estimate has no such weight.
Why the distinction earns you money
The argument that costs tradespeople money almost always has the same shape. A price was given, the job grew, and nobody wrote down which of the three documents the original figure was.
Two habits fix most of it:
- Label the document. If it says Estimate, nobody can later insist it was a fixed price.
- Write the assumptions down. "Assumes existing pipework is sound" is one line, and it is the line you will point at.
Turning one into the other
The usual sequence is estimate or quote first, acceptance second, invoice third. What matters is that the invoice matches what was accepted: the same lines, the same figures, with any variation shown separately rather than folded quietly into a total.
A customer who can see that the invoice is the document they agreed to, plus two clearly marked extras, pays it. A customer handed a larger number with no explanation rings you instead.