Can AI help run a UK plumbing and heating business?

Guide for your tradeUKChecked 29 October 202623 primary sources8 min readUS version

The short answer

Yes. Greymill gives a UK plumbing and heating business 16 AI specialists who share one memory of the firm. They work out call-out and quote prices, draft invoice chasers and enquiry follow-ups for you to send, and raise Gas Safe, ACS, scheme and landlord certificate dates before they fall due. Greymill files and sends nothing until you press Send yourself.

What should my call-out fee and hourly rate be?

Build the rate from the hours you bill, not the hours you pay. Travel, merchant runs, quoting and return visits are paid but never billed.

Divide your loaded hourly cost by utilisation, add overheads per billable hour, then divide by one minus your target margin. In an indicative example, three engineers on £18.00 basic with 25% on-costs, 2,000 paid hours each, 65% utilisation and £180,000 of overheads break even at £80.77 an hour, so a 20% net margin needs about £101. State the call-out fee, and what it covers, before you attend: where no price was agreed, a homeowner owes only a reasonable price (Consumer Rights Act 2015, s.51). See the Academy lesson on charge-out rates and how to price a quote.

How do I chase an unpaid invoice?

A business customer, such as a letting agent or builder, owes statutory interest and fixed compensation on a late invoice. A homeowner does not, so there you send a letter before claim and then use the small claims track.

Under the Late Payment of Commercial Debts (Interest) Act 1998, interest is 8% a year over the reference rate, 11.75% for debts falling due from July to December 2026, plus £40, £70 or £100 per invoice by size (s.5A) (As of Oct 2026). For a homeowner, the Pre-Action Protocol for Debt Claims gives 30 days to reply (para 3.4), and the small claims track in England and Wales covers claims up to £10,000 (CPR r.26.9, As of Oct 2026). See a solicitor before you sue above that limit or if the customer disputes the work. More in how to chase an unpaid invoice and the Academy lesson on cash flow.

How should I follow up enquiries and quotes?

Send a written price with options, such as repair, replace and upgrade, with the guarantee, then follow up at 2 and 7 days.

Fake reviews and misleading claims are banned (Digital Markets, Competition and Consumers Act 2024, Part 4). Say "Gas Safe registered" only with a current number, and "MCS certified" only for technologies you are certified for. See how to follow up enquiries and the Academy lesson on landlord work.

Which registrations and renewals must not lapse?

Gas Safe registration renews every year and each engineer's ACS assessment every 5 years. An engineer works only within the categories on their Gas Safe ID card (Gas Safety (Installation and Use) Regulations 1998, reg 3(1)).

Any business doing gas work must be on the Gas Safe Register (reg 3(3)); breach can mean an unlimited fine or up to 2 years' imprisonment on indictment (Health and Safety at Work etc. Act 1974, s.33 and Sch 3A). Diarise G3 for unvented cylinders over 15 litres, MCS and F-gas certificates too. In England and Wales a new or replacement gas boiler is notified within 30 days of completion (Building Regulations 2010, reg 20), and building control can serve a notice up to 10 years after completion (Building Act 1984, s.36(4)). The Academy lesson on registrations covers each one.

What do I owe landlords on gas safety records?

The duty is the landlord's; yours is a correct record on time. Each appliance and flue the landlord provides is checked at intervals of no more than 12 months, and a check in the 2 months before the due date keeps the anniversary (Gas Safety (Installation and Use) Regulations 1998, regs 36 and 36A).

Existing tenants get a copy within 28 days, new tenants before moving in. Never backdate a record or issue one without a visit: that risks prosecution and removal from the register. Log each failed visit and notice with its date: that is the landlord's evidence of all reasonable steps (reg 39).

Can my customer get a Boiler Upgrade Scheme grant?

In England and Wales, yes, if the home and heat pump qualify and an MCS-certified installer applies. As of Oct 2026 it gives £7,500 towards an air-to-water or ground source heat pump, and £9,000 until 31 March 2027 where an off-gas-grid home replaces oil or LPG.

You deduct the grant from the price. Ofgem's voucher lasts 3 months for air source and 6 for ground source, and Ofgem pays you only after the job, once it approves your redemption, so never order kit on an application alone (As of Oct 2026). Scotland uses Home Energy Scotland grants and loans instead.

Which VAT rate do I charge, and when does CIS apply?

Installing heat pumps, solar, batteries, insulation and heating controls in homes is zero-rated to 31 March 2027, then 5% (Value Added Tax Act 1994, Sch 8 Group 23) (As of Oct 2026). Repairs, boiler swaps and bathrooms are 20%; a gas or oil boiler gets 5% only on a grant-funded job for a qualifying customer (Sch 7A Group 3).

Materials count towards the £90,000 VAT registration threshold (As of Oct 2026). Installing heating, water or drainage for a builder is a construction operation (Finance Act 2004, s.74), so the payer deducts 20% of your labour if you are registered, 30% if not (As of Oct 2026); homeowner work is never under CIS. See the Academy lesson on VAT by job.

Are my engineers employed or self-employed?

How the work is really done decides it, not the CIS card. In Pimlico Plumbers v Smith [2018] UKSC 29, a plumber taxed as self-employed, with a leased branded van, was still a worker, because he worked personally under tight control.

Workers get holiday pay and the minimum wage. Check the right to work before day one: the civil penalty is up to £60,000 per illegal worker (As of Oct 2026). A trainee works on gas only under close supervision by a registered engineer who holds the category (reg 3(1)). See the Academy lesson on engineers' status.

Greymill

How Greymill helps

Explain the firm once, connect Xero or QuickBooks and Outlook, and ask in your own words.

  • Cash & Profit works out your hourly rate, call-out fee and plan prices, and shows who owes you what.
  • Sales & Quotes writes quotes and follow-ups; Writing drafts chasers in your tone.
  • Rules & Licensing lists the dates you must not miss, such as Gas Safe, ACS, scheme and landlord dates, and your overnight brief raises renewals before they are due.
  • Tax & Bookkeeping answers which VAT rate and CIS deduction apply; Staff & HR covers status, pay and holiday.

Greymill only changes your books when you press Approve, and an email goes only when you press Send. Greymill files nothing unless you send it yourself, owes no professional duty, and says when a regulated professional must sign something off. Try it free for 7 days with full Scale access, no card needed; plans start at £100 a month plus VAT. See pricing, how it works and plumbing, heating and electrical.

Start free trialHow it works7 days free with every specialist. No card needed.

Questions owners ask

Can a customer cancel a boiler I sold on a repair visit?

Usually, yes. An urgent repair the customer asked for carries no cancellation right, but a new boiler sold on that visit keeps the 14-day right (Consumer Contracts Regulations 2013, regs 28 and 30). Give the cancellation notice in writing.

Can Greymill sign a gas safety record or certificate?

No. The registered engineer who did or supervised the work signs it. Greymill files nothing unless you send it yourself and owes no professional duty; it drafts wording, such as a warning notice, for you to check.

How much does Greymill cost for a UK plumbing business?

Plans start at £100 a month plus VAT. Starter has 4 specialists, Growth 10 and Scale all 16. Every account starts with a 7-day free trial on full Scale access, with no card needed.

Is my business data used to train AI?

No. Nothing you share is used to train AI, and your conversations are not visible to other customers.

Sources

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