Does CIS Apply to Wood Burner Installers? What to Check Before You Take On Contractor Work

A fair few installers hear "CIS" and assume it's something for groundworkers and roofers, not someone fitting a stove in a customer's living room. For most of your work, that instinct is right. But it stops being right the moment you take a job through someone else's business rather than direct from the homeowner, and getting it wrong isn't a small mistake — HMRC can charge penalties on top of the tax you should have deducted.

The rule that decides almost everything: who's paying you

CIS only applies to payments between businesses in construction. It does not apply to payments from a private householder. If Mrs Patel calls you directly, agrees a price, and pays your invoice from her own bank account, that job sits entirely outside CIS — no registration, no deductions, no returns, regardless of how big the job is or whether you employ staff.

The scheme switches on when the person paying you is a contractor themselves — a builder, a kitchen or bathroom fitting company, a new-build developer, a shopfitter subcontracting you flue work, or a letting agency managing renovations across a property portfolio. It can also apply to a business outside construction that has spent more than £3 million on construction work over the previous 12 months — a hotel chain refurbishing several sites, for example. HMRC calls these "deemed contractors," and the rule catches people who don't think of themselves as construction businesses at all.

So the practical question isn't "am I a stove installer" — it's "who signs my invoice." Direct-to-homeowner work: no CIS. Work through a builder, developer, or a business fitting you into a bigger renovation: check CIS every time.

What counts as "construction operations" for heating work

CIS covers installation of heating systems in a building, and HMRC's guidance specifically lists central heating, hot air convection, and storage heating among the examples. Where it gets genuinely fuzzy for our trade is flues and chimneys specifically — HMRC's published examples don't call out wood burners or flue liners by name, so there's no clean yes/no answer sitting in a manual. If you're doing full heating installations as part of a new-build or renovation contract, treat it as covered and ask the contractor how they're handling deductions before the first invoice goes out. If you're only servicing or repairing an existing system, that's more straightforward: CIS explicitly excludes repairs and maintenance, so swapping a defective baffle plate or resealing a flue joint on an existing installation isn't a construction operation in the way a full install is. Complete replacement of a system, rather than a repair to part of it, is treated as installation and brought back into scope.

If a contractor tells you a job is covered, don't argue the point to save five minutes of admin — get it in writing and move on. If you're not sure either way, a five-minute call to your accountant costs a lot less than an HMRC compliance check.

What registering actually means day to day

If you take on CIS work as a subcontractor, the contractor paying you has to verify your status with HMRC before the first payment, and that verification sets your deduction rate:

• 20% — the standard rate for subcontractors registered with HMRC for CIS.

• 30% — the rate applied if you're not registered, or HMRC can't verify you. This is a real cash flow hit if you didn't see it coming: a £3,000 invoice comes back as £2,100.

• 0% (gross payment status) — available once you've built a track record with HMRC, meaning you're paid in full and settle your own tax and National Insurance through Self Assessment as normal. It has to be applied for and HMRC checks your compliance history first, so it's not something you can request on your first CIS job.

Whatever rate applies, the deduction is a payment on account of your eventual tax bill, not an extra cost — it comes off what you'd owe at year end. The admin burden is what catches installers out: keeping every CIS payment and deduction statement, reconciling them against your own tax return, and — if you ever bring on your own subcontractor labour for a busy stretch — registering as a contractor yourself and filing monthly CIS returns for what you pay them.

The trap most installers actually fall into

It's rarely the big new-build contract that causes problems — those come with a paper trail and a project manager who already knows the rules. It's the smaller, informal arrangement: a local builder who calls you in on three or four jobs a year to fit a stove as part of a wider renovation, paid on his invoice rather than the homeowner's. That's CIS work. If neither of you flags it at the time, it tends to surface later as an unexplained gap when the builder's own CIS returns don't match what he's actually paid out, and untangling it after the fact is far more painful than sorting it up front.

The same applies in reverse if you ever hire a second fitter to help you get through a busy autumn. The moment you're paying someone else for construction work on jobs you've taken on, you're a contractor under the scheme too, with your own verification and deduction obligations.

Keeping the paper trail straight

Whichever side of it you're on, CIS comes down to knowing, job by job, who you were paid by, whether it was a private customer or a business, and what (if anything) was deducted. That's easy to lose track of when it's spread across a diary, a stack of invoices, and a bank statement — and it's exactly the kind of detail that's obvious in hindsight but easy to miss when you're quoting the next job. In BurnerCRM, every job carries its own record from first enquiry through to invoice, so you've got a clear log of who a job was for and what was paid, without digging back through old paperwork when your accountant asks. You can see how it fits alongside the rest of your job tracking at burnercrm.co.uk.

If you're currently doing a mix of direct homeowner work and jobs through builders or developers, it's worth a genuinely quick check with your accountant on where your existing contracts sit — better to fix it now than after a return's already gone in.