CIS deductions and refunds, van and tool costs, mileage, PPE, VAT and MTD for Income Tax explained for self-employed garage door fitters and installers.
A self-employed garage door fitter runs a small, kit-heavy business on the back of a van. One day you are fitting an anthracite sectional door to a new-build for a developer, the next you are swapping a tired up-and-over for a homeowner who found you on a local trade site. Those two jobs are taxed in noticeably different ways, and getting the distinction right, especially around the Construction Industry Scheme, is where most fitters either overpay or land an unexpected bill.
This guide is built around how a fitter actually earns and spends: CIS deductions and the refunds they usually trigger, the van and tooling costs that dominate your expenses, mileage between jobs, materials when you supply and fit, and the VAT reverse charge that catches out construction trades. Keep clean records as you go and the annual return becomes a quick reconciliation rather than a January scramble.
As a sole trader you pay Income Tax on profit, which is your installation income minus allowable expenses. For 2025/26 the personal allowance covers the first GBP 12,570, then you pay 20% to GBP 50,270, 40% to GBP 125,140 and 45% above, with the personal allowance tapering away between GBP 100,000 and GBP 125,140 to create an effective 60% band. Class 4 National Insurance is 6% on profit between GBP 12,570 and GBP 50,270 and 2% above, with Class 2 NIC settled through Self Assessment.
Scottish fitters pay Scottish Income Tax on their profit through six bands (19%, 20%, 21%, 42%, 45% and a 48% top rate) and carry an S-prefixed tax code, while National Insurance stays UK-wide. Welsh fitters have a C-coded tax code at rates currently matching the rest of the UK. CIS subcontractors should keep an eye on their code, because deductions taken at source can sit oddly against any PAYE income; if your code looks wrong, run it through the tax code checker.
If you fit doors as a subcontractor for a builder, developer, property maintenance firm or main contractor, your work falls under the Construction Industry Scheme. The contractor is legally required to verify you with HMRC and deduct tax from the labour element of your invoice before paying you. The standard deduction is 20% if you are registered with CIS, or 30% if you are not, so registering is almost always worth it.
The key point is that CIS deductions are not your final tax bill. They are taken from your labour before any personal allowance or expenses are applied, so by year-end you have almost always overpaid. When you file, you total your real profit after van, tool and material costs, work out the actual tax due, and HMRC repays the excess CIS already deducted. For many fitters this means a yearly refund running into hundreds or thousands of pounds. Our CIS subcontractor guide explains registration, deduction statements and the refund mechanics in full, and you can estimate your position with the CIS tax calculator.
Work you carry out directly for a private homeowner is outside CIS, so nothing is deducted and you are responsible for the full tax on that profit. Most fitters have a mix of both, which is exactly why clean records of who deducted what matter.
| Who you invoice | CIS applies? | What happens |
|---|---|---|
| Builder, developer or main contractor | Yes | 20% deducted from labour (30% if unregistered) |
| Property maintenance or facilities company | Usually yes | Deduction taken; keep the CIS statement |
| Private homeowner direct | No | Full payment received; you account for all tax |
| Supplying materials separately | No on materials | Deduction applies to labour only, not the door cost |
An expense is allowable when incurred wholly and exclusively for the business. For a fitter the list is dominated by the van, tooling and materials rather than office costs.
| Expense | What qualifies | Notes |
|---|---|---|
| Van running costs | Fuel, insurance, road tax, servicing, repairs, tyres | Or claim simplified mileage instead, not both |
| Power and hand tools | Drills, impact drivers, SDS, levels, rivet guns, snips, batteries | Usually claimed in full via the Annual Investment Allowance |
| Consumables and fixings | Drill bits, plugs, screws, rivets, sealant, lubricant | Fully deductible as used |
| Materials (supply and fit) | Doors, motors, track, springs, spindles, remotes | Deductible; also counts towards VAT turnover |
| Access equipment | Ladders, steps, work platforms, towers | Tools claimed via AIA |
| PPE and workwear | Safety boots, gloves, knee pads, goggles, hi-vis, logo'd uniform | Protective and branded clothing only |
| Insurance | Public liability, tool cover, van insurance | Trade-related cover is deductible |
| Phone and admin | Business share of mobile, quoting software, fuel cards | Apportion private use out |
| Trade membership | Relevant trade association or installer scheme fees | Allowable where work-related |
| Accountancy and bank fees | Bookkeeping, Self Assessment, business banking | Fully deductible |
Your vehicle is usually the single largest running cost. You have two methods and must pick one per vehicle. The simplified mileage method lets you claim a flat 45p per mile for the first 10,000 business miles in the year and 25p thereafter, with no need to track fuel and servicing separately, which suits a fitter racking up site-to-site miles. Alternatively you claim the actual proportion of total running costs (fuel, insurance, tax, repairs, depreciation) that relates to business use. A fitter with a dedicated van and high running costs often does better on actual costs, while someone with a newer, efficient van and lots of mileage may prefer the flat rate. Run both once and keep the larger. Travel from home to a temporary site is generally allowable; ordinary commuting to a fixed base is not.
Safety boots, gloves, knee pads, goggles and hi-vis are protective equipment and fully deductible, as is workwear carrying your business logo. Everyday clothing you happen to wear to work is not. Tools and equipment bought outright, from a new SDS drill to a folding work platform, are normally claimed in full in the year of purchase through the Annual Investment Allowance, so a year you re-kit can produce a sizeable deduction.
The private share of your van, phone and any dual-use kit must be excluded. Ordinary clothing is never allowable even if you only wear it on jobs. Fines and parking penalties are not deductible, though genuine business parking and tolls are. And the cost of training into a brand-new trade is not allowable, whereas a course updating your existing installation or electrical-competence skills is.
Take a fitter working mainly as a CIS subcontractor for two local builders, with a few direct homeowner jobs, invoicing GBP 46,000 of labour and materials across the year.
Income: GBP 46,000 (CIS labour GBP 34,000, direct homeowner work GBP 6,000, materials recharged GBP 6,000)
CIS already deducted: GBP 34,000 labour at 20% = GBP 6,800 withheld during the year
Allowable expenses:
Taxable profit: GBP 46,000 minus GBP 15,400 = GBP 30,600
Income Tax: GBP 30,600 minus GBP 12,570 = GBP 18,030 at 20% = GBP 3,606
Class 4 NIC: GBP 18,030 at 6% = GBP 1,082
Tax and NIC due: GBP 4,688. Because CIS already deducted GBP 6,800, the fitter is owed a refund of around GBP 2,112 once Class 2 is added in. That gap is exactly why CIS subcontractors should never assume the deductions are their final bill. Run your own figures through the sole trader tax calculator or the CIS calculator to estimate your refund.
For a garage door fitter under CIS, the deduction on your invoice is a deposit, not a settlement. Track every expense and every CIS statement and the refund is usually waiting for you.
You must register for VAT once taxable turnover passes GBP 90,000 in any rolling 12-month period. A supply-and-fit fitter reaches this faster than a labour-only subcontractor, because the door, motor and track materials all count towards turnover, not just your labour. Once registered, the construction industry domestic reverse charge usually applies when you invoice another VAT-registered contractor: you do not charge them VAT, you note that reverse charge applies, and they account for it. This was introduced to stop VAT fraud in construction and it catches out fitters who keep charging VAT as normal. Reverse charge does not apply to work for a private homeowner, where you charge VAT in the usual way. If most of your work is for builders, factor the reverse charge into your invoicing software before you register.
Making Tax Digital for Income Tax Self Assessment replaces the annual return with quarterly digital submissions and a year-end finalisation. The thresholds are based on gross income, not profit, which for a CIS subcontractor means your turnover including the labour figure before any deduction:
For a fitter this is a real change of habit. Instead of bagging up CIS statements, fuel receipts and material invoices once a year, you record each job and cost digitally as it happens and send HMRC a summary every quarter using MTD-compatible software. The upside is that your CIS deductions and refund position become visible through the year rather than a surprise at filing. Our guide to MTD for sole traders walks through the quarterly rhythm in practice.
Treating CIS deductions as the final tax. They are advance payments only. Without filing a return that claims your expenses, you leave your refund with HMRC.
Not registering for CIS. Staying unregistered means 30% deducted instead of 20%, tying up more of your cash all year for no benefit.
Losing CIS deduction statements. You need the contractor's monthly statements to prove what was withheld; reconstruct them now, not next January.
Mixing the van methods. You cannot switch between mileage and actual costs for the same vehicle within its life. Pick one and stick with it.
Ignoring the VAT reverse charge. Carrying on charging VAT to a contractor when reverse charge applies creates a mess that has to be unwound.
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