Fitted Isn't Finished: Agreeing What 'Completion' Means Before You Pay the Balance

There's a moment in every window job where the fitter wipes his hands, says "that's you done, then", and produces a card reader. It usually happens while you're still on your knees peering at a mastic line, and it always feels a bit rude to say "hang on, can I have a proper look first?". So most people just pay.

Here's the thing, though: your quote almost certainly says the balance is payable on completion, and it almost certainly never defines what completion means. That single vague phrase is responsible for a surprising number of the awkward phone calls that follow a window install. Not because anyone's out to fleece you — just because "done" means something different to the person holding the silicone gun than it does to the person who has to live with the result for the next twenty-five years.

What your quote probably says — and what it leaves out

Have a look at the payment terms on your quote. Nine times out of ten you'll see something along the lines of a deposit now, balance on completion, maybe a third line about "final payment due upon satisfactory installation". That last one sounds reassuring until you realise that "satisfactory" is doing an enormous amount of unpaid work in that sentence. Satisfactory to whom? Judged when? By what standard?

For the installer, completion often means the frames are in and the van is loaded. For you, it probably means the windows work, the house is watertight, the mess is gone, and you've got the paperwork in your hand. Those are two quite different finish lines, and the gap between them is where the arguments live.

Five different things all hiding behind one word

When people say a window job is "finished", they're usually bundling together five separate milestones:

• Frames fixed — the units are in the openings and screwed or strapped home.
• Glazed and operational — glass in, handles turning, hinges adjusted, vents opening, locks engaging.
• Sealed and made good — internal and external sealant applied, trims on, plasterwork and sills tidied to whatever standard you agreed.
• Snagged — the walk-round done, defects written down, and a date agreed for putting them right.
• Paperwork handed over — guarantee documents, the competent person certificate (FENSA or equivalent), care instructions, and confirmation that old frames and glass have gone to a licensed waste route.

A job can be at stage one and still three weeks from stage five. So when the card reader appears, it's worth knowing exactly which of those five you're being asked to pay for.

Why paying early quietly costs you leverage

Nobody likes to think of themselves as a difficult customer, and I'm not suggesting you should be one. But there's a hard commercial fact here: money is the only real lever you hold in a domestic building job. Up until the moment you pay, you're a customer with a query. Afterwards, you're a caller in a queue — a polite, well-meaning caller, but a caller nonetheless.

That's not a slur on window firms. It's just how any business prioritises a to-do list. A snagging visit that's already been paid for will always sit behind a job that hasn't.

Put your own definition in writing

You don't need a solicitor for this. You need one extra line on the order form, agreed before you sign — ideally by email so there's a record. Something like:

"Completion, for the purposes of final payment, means: all windows installed, glazed and fully operational; internal and external sealing complete and cured; snagging list agreed in writing and a remediation date set; all waste and old frames removed; and all certificates, guarantee documentation and care instructions handed over."

Will every firm accept it? Most reputable ones won't blink. A few will push back, and that in itself tells you something useful about how they handle aftercare. If a company won't put its own standard of completion in writing, ask yourself why.

Run the snagging walk-round like you mean it

Do this in daylight, with the fitter still on site if at all possible — it's far easier to point at a problem than to describe it down a phone a fortnight later. Take a torch, a cloth, and a roll of masking tape to flag anything you spot.

Open and close every window. Turn every handle, throw every lock, check every trickle vent slides. Look along the mastic lines — they should be smooth and continuous, not smeared or gappy at the corners. Check the drainage slots at the bottom of the frames aren't blocked with swarf. Look at the reveals and the sill from outside as well as in. Run a hand around the frame for draughts on a windy day if you can arrange it.

Write your list down, date it, and get a copy to the firm the same day. A snagging list sent by email within 24 hours is very hard to dispute later.

Retention: a small hold-back, agreed in advance

In commercial construction, retention is standard — a percentage held back for weeks or months after practical completion. For a domestic window job you're unlikely to get a formal 5% retention clause unless you ask for it, but a modest hold-back discussed before signing is often acceptable.

Something like five per cent held for fourteen days after the snags are put right gives everyone a reason to close the job out cleanly. Don't spring it on the day; that reads as hostility. Raise it at quote stage and see how they respond.

If a firm won't agree to any hold-back, there are other ways to protect yourself. Pay the balance by credit card where you can — anything over £100 gets Section 75 protection. Or agree staged payments tied to the five milestones above, rather than one lump at the end.

The phrases that should make you pause

• "The office needs it today for the paperwork."
• Card reader out before you've had a chance to look round.
• "We'll come back for the mastic once it's settled."
• No certificate, "but it's all logged on the system".

None of these are automatically dodgy. But they're all reasons to say, pleasantly, that you'll settle up once the walk-round's done.

Before you tap the card

Tick off the boxes: every window opens and locks, sealing finished inside and out, snagging list written and shared, waste gone, certificate and guarantee in your hand. Then pay — promptly, and with a thank-you. That's the deal. Just make sure "completion" means the same thing to both of you before the money moves.