The four clocks a UK plumbing business has to run

Four dates govern a UK plumbing business, and not one of them was chosen by the person running it. The gas safety check on a rented property falls due at 12 months. The record has to reach the tenant within 28 days of the check. The VAT invoice has to leave within 30 days of the supply. And the money arrives some time after that — but only after the invoice, which means the one clock you control is the one most businesses start last.

Plumbing job management software earns its keep on exactly those four, and nowhere else. Everything else it does — quoting, scheduling, photographs on the job — a diary and a phone will manage badly but will manage. A missed regulation 36 deadline is not a scheduling inconvenience; it is your customer in breach and your name on the record that proves when the clock started.

Clock one: twelve months, and it does not reset

Regulation 36(3) of the Gas Safety (Installation and Use) Regulations 1998 requires a landlord to ensure that each appliance and flue "is checked for safety within 12 months of being installed and at intervals of not more than 12 months".

"Not more than" is doing the work in that sentence. A check carried out late does not buy the landlord a later anniversary; it means the previous interval was already too long. This is the duty that quietly makes a plumbing business into a recurring-revenue business, because every landlord property you touch generates a date twelve months out — and the business that holds those dates in a system rather than in somebody's head is the one that gets the call. What regulation 3 requires of the engineer doing the work, rather than of the landlord, is set out in what regulation 3 actually requires of you.

Clock two: twenty-eight days to the tenant, or before they move in

Regulation 36(6) sets the second deadline, and it has two limbs:

a copy of the record made pursuant to the requirements of paragraph (3)(c) above is given to each existing tenant of premises to which the record relates within 28 days of the date of the check

and, for anyone moving in, "a copy of the last record made in respect of each appliance or flue is given to any new tenant of premises to which the record relates before that tenant occupies those premises".

The duty is the landlord's, not yours. But the 28 days run from the date of the check, which is a date only you know, recorded on a document only you produce. A plumbing business that emails the record the same evening has handed the landlord 28 clear days. One that batches paperwork on a Friday has already spent four of them. The nine items the record itself has to carry, and the way the anniversary behaves, are in the landlord gas safety record: nine items, twenty-eight days, and the rule that stops the date drifting.

Clock three: thirty days to the VAT invoice

Regulation 13 of the Value Added Tax Regulations 1995 is short and absolute: the documents "shall be provided within 30 days of the time when the supply is treated as taking place."

Thirty days from the supply — not from the day the job sheet came back from the van, and not from the day somebody had time. For a plumbing business running emergency callouts this is the clock most often breached without anybody noticing, because nothing bounces. The invoice simply goes out on day 40 and nobody writes to say so.

The 5 percent nobody charges

Here is the part that changes a quote rather than a filing date, and it is the most under-used rule in UK domestic plumbing.

VAT Notice 708, section 2.1, puts "renovation or alteration of empty residential premises" at 5 percent, and "conversion (other than for housing associations) of a non-residential building into a qualifying dwelling or communal residential building and conversions of residential buildings to a different residential use" at the same 5 percent. Section 2.2 then adds the sentence that decides whether it is worth the paperwork: "if their work is zero-rated or reduced-rated, then so are the 'building materials'."

A full bathroom and heating replacement in a house that has stood empty for two years is a 5 percent job including the boiler, the cylinder, the radiators and the tiles — not a 20 percent job with a 5 percent labour element. On a £14,000 install that is £700 of VAT rather than £2,800 — the customer keeps £2,100.

Two practical points sit behind it. The two-year test is about the building, not about the customer: you are relying on a fact you cannot see, so the evidence — an empty homes officer's letter, council tax records — belongs on the job record from the day you quote, not in a folder you build if HMRC asks. And a quoting tool that holds one rate per document cannot price this job at all without splitting it, which is why the rate belongs on the line.

Clock four: the one that only starts when you do

The payment clock is the only one of the four with no statute setting its length — and the only one with money attached at the end. It begins with the invoice, which is why clocks three and four are really one clock seen from two sides. What you are entitled to when it runs out, and the fixed sums that come on top of the interest, are set out in the weekly run, in order.

When you work for a contractor rather than a householder, one more thing has to be settled before the invoice can even be right: whether VAT goes on it at all. HMRC's technical guide is explicit that "the reverse charge does not apply for supplies to end users when the end user tells their supplier or building contractor in writing that they're an end user", and that a small reverse-charge element can be ignored — "if the reverse charge part of the supply is 5% or less of the whole supply value this can be disregarded". Both of those are facts about a customer, held once and applied to every job for them; the full set is in when your invoice must not show VAT.

What the market charges, and the trap in comparing it

Two pricing shapes are on sale in the UK, and for a plumbing business the difference is larger than the headline figures suggest. Checked on 21 September 2026: Tradify lists Lite, Pro and Plus at £34, £37 and £44 per user per month, with a 14-day free trial and no statement either way about VAT on the page. ServiceM8 lists Starter, Growing, Premium and Premium Plus at £25, £59, £119 and £269 per business with unlimited users — and meters them by jobs per month: 50, 150, 500 and 1,500.

For a plumber that metering is the whole decision, because a plumbing business is job-heavy by nature. Twelve landlord safety checks in a week is twelve jobs. A single bathroom is one. Two businesses with identical turnover can sit three plan tiers apart, and the one doing reactive and landlord work is always the one paying more.

Five things to set up before the next landlord job

1. Record the date of the check as a field, not as a line in a report. Both clock one and clock two are measured from it.
2. Send the record the same day. It costs nothing and hands the landlord the full 28 days instead of what is left of them.
3. Put the next check on the calendar at the moment you finish this one, twelve months out. This is the entire recurring-revenue mechanism in one step.
4. Ask the two-year question at quoting time, and store the answer with its evidence against the property. Nobody remembers it at invoicing.
5. Hold the end-user statement against the customer, not against the job. It applies to all of their work until they withdraw it.

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Position as at 21 September 2026, checked against regulation 36 of the Gas Safety (Installation and Use) Regulations 1998, regulation 13 of the Value Added Tax Regulations 1995, VAT Notice 708 and HMRC's reverse charge technical guide as published on that date. It describes the position in Great Britain and is not legal or tax advice. The figure most likely to move is the 5 percent band: the reduced and zero rates for construction are set by Schedules 7A and 8 of the VAT Act 1994 and have been amended repeatedly, most recently for energy-saving materials — check section 2.1 of Notice 708 for the current table before you quote a job at anything other than 20 percent.

What Zirko does here: it keeps the date of a check, the record produced on that date, the photographs and the invoice on the same job, so that the twelve-month follow-up is a consequence of finishing the work rather than a separate act of remembering. What Zirko does not do: it does not decide whether a dwelling has been empty for two years, it does not issue or lodge gas safety records, and it is not on the Gas Safe Register — the record is yours and the registration is yours.