How to quote for a job you have not seen
Somebody rings and wants a number. They cannot get you round until next week and they would like an idea now, and the idea is that you say something.
Saying nothing loses work. Saying a figure loses money. The way through is not to refuse, it is to say something that is genuinely useful and is structurally not a quote.
What a number on the phone becomes
Whatever you say, the customer hears a price and remembers the lower end of anything you said. That is not dishonesty, it is how people listen when they are hoping for good news.
Worse, if it sounds firm it may be an offer they can accept. A quote a customer accepts is generally a contract, and "I said that before I had seen it" is a weak position rather than an obvious defence.
So the goal is a figure with the uncertainty attached to it, in the same breath, in a form they will still remember next week.
A range, called a range
"Something between two and a half and three and a half, but I would need to see it before I could be firm."
Three things make it work. The width tells them honestly how uncertain you are, which is information they want. The word range means it will not be mistaken for an offer. And saying what would narrow it, which is a visit, moves straight to the thing you actually want.
Make the range genuinely wide where the job is genuinely uncertain. A narrow range on a job you know nothing about is a quote with a small hedge, and it will be treated as one. If the honest answer is "anywhere from two to six thousand depending on what is behind that wall", say that. Customers respect it more than trades expect, and it is a better filter than any qualification: the person who is fine with that range is a person worth visiting.
Follow the call with an email
This is the part that matters and it takes a minute.
"Good to speak. As discussed, likely somewhere between £2,500 and £3,500 depending on the condition of the existing pipework and whether the floor needs lifting. Not a quote, and I would want to see it before giving you a firm figure. Free to come Thursday morning if that suits."
Now the range exists in writing, with its reasons, and with the word "not a quote" in it. It also converts the call into a booked visit, which is the whole point of the exercise.
Provisional sums, for the part you cannot see
Sometimes you have seen most of a job but not all of it. The bathroom is obvious; the state of the joists is not.
The construction answer is a provisional sum: a line in the quote with an allowance for the unknown part, marked as an allowance, to be adjusted to the real cost once it is exposed.
"Allowance for joist repair: £600. This is provisional. Once the floor is up I will confirm the actual figure before proceeding." The customer gets a total they can budget against, you are not carrying a risk you cannot price, and the adjustment is expected rather than being a variation you have to negotiate from a standing start.
Keep provisional sums to genuine unknowns. A quote where half the lines are provisional is not a quote, and a customer will read it, correctly, as somebody who has not worked out what they are doing.
Charging for the survey
Where visits are eating your week, there is a middle option between quoting blind and driving out for free.
Charge for the survey, and credit it against the job if they proceed. "The survey is £90, which comes off the price if you go ahead." A customer who is serious does not mind. A customer collecting five free quotes goes elsewhere, which is the point.
It works best where the survey genuinely produces something: a written report on the state of the wiring, a schedule of what needs doing in what order, a fixed price nobody else could give without the same work. If all they get is your number then charging for it feels like a fee for the privilege of being sold to, and it will read that way.
It also changes the conversation on the phone. "I can give you a range now and a firm price after a survey, which is £90 and comes off the job" gives them a real choice, and the person who takes it has already spent something, which makes them considerably more likely to proceed.
When you have to commit blind
Occasionally there is no visit. Insurance work, a landlord in another county, a job small enough that a visit costs more than the margin.
Two protections. Price the pessimistic version rather than the likely one, because you are being paid to carry a risk you cannot inspect, and that is what carrying it looks like. And write the assumptions in hard: what you are assuming about access, condition, parking, power, what is already there. Assumptions are what turn a fixed price into a conditional one, and a condition that is not met is the legitimate reason a price moves.
And send it as an estimate rather than a quote, deliberately, with the word at the top.