What a plumbing invoice has to record

Reported, found, fixed

The customer called about no hot water. You found a failed diverter cartridge. You replaced it and rebalanced the system. An invoice that says only “replace diverter cartridge” describes one third of that, and it is the third the customer understands least.

Put the reported fault on the document in the customer’s own words, then what you found. It costs one line and it does three jobs: it proves you were called out for a real problem, it explains a part they have never heard of, and — the one that matters — it means that if the same symptom comes back in March, both of you can see whether it is the same fault or a new one.

A landlord reading it six months later gets the same benefit, and so does the next plumber.

Supply and fit, fit only, supply only

The convention that carries most of the meaning on a plumbing invoice is the phrase in front of the part.

• Supply and fit — you provided the part and installed it. One line, one price, and the part is yours to stand behind.
• Fit only — the customer bought it. Say so on the line, because a fitting you did not choose is a fitting whose failure is not your workmanship. This is the single most useful five words on the document the day a bargain mixer starts dripping.
• Supply only — you dropped a part off and somebody else fitted it. Rare, and worth writing plainly when it happens.

Describe the part well enough to be recognised: type, size, and the fitting standard where it matters. “Flexible connector, 15mm, pair” is checkable. “Parts” is a number with no argument attached to it.

Put the times on out-of-hours work

A premium rate is justified by when you attended, so the document should say when you attended. The attendance time — arrived 20:10, left 21:35 — turns an evening rate from an assertion into a record, and it is the first thing a letting agency asks for when a landlord queries the bill.

The rate structure behind those hours is a separate question, and invoicing a plumbing job covers the three normal ways to charge for turning up.

Record the work you did not do

Plumbers see things. A seized valve, a weeping joint on a pipe you were not called about, a flue that somebody should look at. The invoice is the document the customer keeps, so it is the right place for a short further work note — what you saw, that you did not do anything about it today, and a quote reference if you sent one.

Two sentences at the bottom of an invoice settle a surprising number of later conversations, in both directions: the customer who says they were never told, and the customer who assumed a mention in the hallway meant it had been dealt with.

Where plumbing invoices go wrong

• Only the fix. No reported fault, no findings, so the document reads as a part swap at a surprising price.
• No property address on rental work. A landlord with three flats cannot allocate it, so it waits.
• An evening rate with no times. The premium is reasonable; the invoice just does not evidence it.
• Customer-supplied parts fitted silently. You have quietly warranted somebody else’s bargain.
• Nothing about the thing you noticed. Say it on the document, once.

Making the document

The free invoice generator covers this shape: quantity-and-rate lines for labor and parts, a tax rate if you charge one, and a notes field with room for the reported-and-found sentence and the further-work line. It runs in your browser, nothing is uploaded, and the PDF has no watermark on it.

The follow-up work is a quote rather than an invoice, and what goes on an estimate covers that document — including how to write the assumptions for a job where nobody knows what is behind the wall yet. For the electrical equivalent of the same service call, writing up an electrical job deals with device counts and the paperwork an invoice points at.