Decking Installer
Tax & MTD Guide
CIS deductions and refunds, allowable tools and van costs, materials, VAT and MTD for Income Tax explained for self-employed UK decking and landscaping installers.
Estimate your tax as a self-employed decking installer
Adjust the figures to see your estimated Income Tax and Class 4 National Insurance for the year.
Total turnover before expenses
Under £1,000 we use the trading allowance automatically
Estimated tax bill
£3,492
9.7% effective rate for 2026/27
- Income tax
- £2,686
- Class 4 NI
- £806
Take-home pay
£22,508
after tax, NI and expenses
This is an estimate using HMRC-confirmed rates for 2026/27, not your official tax calculation. TapTax is MTD-compatible, so you can connect to HMRC and file the real figures in a couple of taps.
- Decking installation is normally a CIS trade: when you subcontract to builders or landscaping firms they deduct 20% from your labour at source, which usually means a Self Assessment refund once expenses and your personal allowance are applied.
- You are taxed on profit, not turnover, so every van cost, tool, blade, fixing, bag of consumables and bought-in material reduces your bill if you keep the receipts.
- Keep every CIS deduction statement from each contractor; without them you cannot reclaim the tax already taken and may overpay by thousands.
- Track your rolling 12-month turnover toward the £90,000 VAT threshold, and remember the domestic reverse charge changes how you invoice VAT-registered contractors.
- MTD for Income Tax applies from April 2026 above £50,000 of gross income, April 2027 above £30,000 and April 2028 above £20,000, tested on gross turnover before CIS and expenses.
Decking installation is a tools-and-van trade with a tax twist most office-based freelancers never deal with: the Construction Industry Scheme. You quote a job, lay the joists, screw down the boards, and somewhere in that process a contractor has already taken 20% of your labour before the money reaches your account. That changes the whole shape of your tax year. Instead of saving up to pay HMRC each January, most decking fitters have overpaid through the year and are owed money back.
This guide is built around how installers actually earn and spend: CIS deductions and the refund that usually follows, the van, tools, blades and bought-in materials that make up your costs, the record-keeping that turns a shoebox of receipts into a clean refund claim, and the VAT reverse charge that trips up so many trades. Get the CIS statements and receipts in order and the annual return becomes straightforward.
How Tax Works for a Self-Employed Decking Installer
As a sole trader you pay Income Tax on profit, which is your total income from decking and landscaping work minus your allowable expenses. For 2026/27 the personal allowance covers the first £12,570, then you pay 20% to £50,270, 40% to £125,140 and 45% above, with the personal allowance tapering away between £100,000 and £125,140 to create an effective 60% band. Class 4 National Insurance is 6% on profit between £12,570 and £50,270 and 2% above, while Class 2 NIC is settled through Self Assessment.
The key point for a CIS subcontractor is that contractors deduct that 20% from your labour based on turnover, before any personal allowance or expenses are considered. So the tax taken at source is almost always more than you actually owe. Your Self Assessment reconciles the two: you declare your full income, deduct your expenses and allowances, work out the real tax and NIC, then offset the CIS already paid. The result is normally a refund.
Scottish installers pay Scottish Income Tax on profit through six bands (19%, 20%, 21%, 42%, 45% and a 48% top rate) and carry an S-prefixed tax code; Welsh installers have a C-coded code at rates currently matching the rest of the UK. National Insurance stays UK-wide. If a PAYE side job or an old employment is distorting your code, run it through the tax code checker.
CIS: The Part That Defines Your Tax Year
Installing decking, fencing, pergolas, paving and associated groundworks counts as construction operations, so when you work as a subcontractor for a builder, developer or landscaping company, the Construction Industry Scheme applies. They verify you with HMRC and deduct tax from your labour before paying: 20% if you are verified and registered, 30% if you are not. Registering for CIS as a subcontractor and getting verified is the single quickest way to stop losing an extra 10%.
A few important details for decking fitters:
- The deduction is on labour, not materials. If your invoice separates materials from labour, CIS is only taken on the labour element. Always itemise materials separately so the contractor does not deduct 20% from your decking boards, joists and fixings.
- Work direct for homeowners is outside CIS. A private homeowner is not a contractor, so a deck you build directly for a household is paid gross with no deduction. You still declare that income and pay tax on it through Self Assessment.
- Keep every CIS statement. Each contractor must give you a monthly deduction statement showing what they paid and what they took. These are your proof of tax paid; lose them and you cannot reclaim it.
Our full CIS subcontractor tax guide walks through registration, verification and how the deductions flow through to your return.
- CIS deduction statement
- A monthly statement that a contractor must give every subcontractor they pay under the Construction Industry Scheme. It shows the gross amount, the cost of any materials, and the tax deducted (20% for verified subcontractors, 30% for unverified). These statements are your evidence of tax already paid to HMRC. You add them up across the tax year and claim the total as a credit on your Self Assessment, which is what produces the typical CIS refund. Store them digitally as they arrive so none go missing before you file.
Why You Usually Get a Refund
Because CIS takes 20% off your labour turnover before any reliefs, the tax deducted ignores your personal allowance and every penny of your expenses. Once you file and apply them, your real liability is almost always lower than what was taken. HMRC refunds the difference.
A simple way to see it: a fitter invoicing £40,000 of labour has roughly £8,000 deducted under CIS through the year. After the £12,570 personal allowance and several thousand pounds of van, tool and material costs, the actual Income Tax and Class 4 NIC due is far less than £8,000, so a refund follows. The CIS tax calculator lets you estimate your own refund from your turnover and deductions before you file.
Allowable Expenses for Decking Installers
An expense is allowable when incurred wholly and exclusively for the business. For an installer the list is dominated by the van, tools and consumables that keep you working.
| Expense | What qualifies | Notes |
|---|---|---|
| Power tools and hand tools | Impact drivers, drills, track and mitre saws, jigsaws, levels, squares, batteries and chargers | Larger items claimed via the Annual Investment Allowance |
| Blades, bits and consumables | Saw blades, drill bits, decking screws, hidden fixings, post fixings, sealant, packers | Fully deductible as they are used up on jobs |
| Materials bought in | Decking boards, joists, posts, gravel boards, membrane, postcrete bought for client jobs | Deductible; bill clients separately to keep CIS off materials |
| Van and running costs | Lease or purchase, insurance, road tax, MOT, servicing, repairs and fuel | Claim actual costs or use HMRC mileage; not both |
| PPE and workwear | Steel-toe boots, gloves, knee pads, ear and eye protection, branded hi-vis and work trousers | Protective and branded items qualify; ordinary clothing does not |
| Waste and access | Skip hire, tip and waste-transfer charges, scaffold or platform hire | Deductible job costs |
| Insurance | Public liability and tool cover | Trade insurance is allowable |
| Phone and admin | Business share of mobile, quoting and invoicing software, stationery | Apportion any private use |
| Home office | A fair share of running costs for quoting, ordering and bookkeeping at home | Use HMRC's flat rate or an actual proportion |
| Accountancy and bank fees | Bookkeeping, Self Assessment, business banking | Fully deductible |
Van and Mileage: Pick One Method
The van is usually an installer's biggest single cost. You can either claim actual running costs (a fair business proportion of purchase or lease, fuel, insurance, tax, servicing and repairs) or use HMRC's simplified mileage rate of 45p per business mile for the first 10,000 miles and 25p after that. You cannot mix the two for the same vehicle, and once you choose mileage for a van you generally stick with it for that vehicle. For a fitter doing long runs to sites with materials in the back, the actual-cost method often wins; for shorter local jobs, mileage can be simpler and sometimes larger. Work it out both ways once.
What You Cannot Claim
The private share of dual-use costs, your home-to-base commuting, ordinary clothing worn on site, fuel for personal trips, and meals during a normal working day are not allowable. Tools bought before you started trading are pre-trading expenditure, claimed when you begin rather than ignored.
Worked Example: A Decking Installer on £45,000 Turnover
Take a fitter working mainly as a CIS subcontractor for landscaping firms, invoicing £45,000 over the year split between labour and materials.
Turnover: £45,000 (labour £32,000, materials recharged £13,000)
Allowable expenses:
- Materials bought in for jobs: £13,000
- Van running costs and fuel (actual method): £5,200
- Tools, blades, fixings and consumables (incl. AIA): £2,400
- PPE, workwear and insurance: £900
- Skip hire and waste charges: £700
- Phone, home office and accountancy: £800
- Total expenses: £23,000
Taxable profit: £45,000 minus £23,000 = £22,000
Income Tax: £22,000 minus £12,570 = £9,430 at 20% = £1,886
Class 4 NIC: £9,430 at 6% = £566
Total Income Tax and NIC due: £2,452. But CIS already took roughly 20% of the £32,000 labour = £6,400 through the year. Offsetting that against the £2,452 due leaves a refund of around £3,948. Run your own figures through the sole trader tax calculator to sense-check the liability before applying your CIS credit.
For a decking fitter the refund lives in two places: the CIS statements that prove what you paid, and the receipts that prove what you spent. Keep both as they come in and the money comes back.
Record-Keeping That Protects the Refund
Site work is messy and receipts get destroyed. A few habits make the difference between a clean refund and a guess:
- Photograph every receipt the day you get it. Thermal receipts from merchants fade within months, so capture fuel, materials and consumables straight away.
- File CIS statements as they arrive. One per contractor per month; total them at year end as your tax-paid credit.
- Separate labour and materials on every invoice. This keeps CIS off your materials and makes your turnover figures clean.
- Log mileage or fuel consistently. Decide on actual costs or mileage early and record what that method needs.
- Use a separate business bank account. It makes income and expenses obvious and saves hours at year end.
VAT and the Domestic Reverse Charge
You must register for VAT once taxable turnover exceeds £90,000 in any rolling 12-month period. Because installers invoice materials plus labour, that threshold arrives faster than for labour-only trades, so watch your rolling total.
For construction work, the domestic reverse charge usually applies when you subcontract to another VAT-registered, CIS-registered business. Instead of adding VAT to your invoice, you state that the reverse charge applies and the contractor accounts for the VAT to HMRC. It removes VAT from your cashflow on those jobs but means you no longer hold the VAT you used to. Work direct for private homeowners is normal VATable supply, not reverse charge. The rules are fiddly, so take advice before you register or as you approach the threshold.
MTD for Income Tax: What Changes for Installers
Making Tax Digital for Income Tax Self Assessment replaces the once-a-year return with quarterly digital submissions and a year-end finalisation. The thresholds are based on gross income, not profit, and crucially that is gross turnover before CIS deductions:
- April 2026: Combined gross trading and property income over £50,000
- April 2027: Over £30,000
- April 2028: Over £20,000
A busy decking fitter can clear £50,000 of invoiced work even after 20% CIS is taken, so check your gross turnover, not the net amount that hit your account. Under MTD you record each invoice, material purchase and van cost digitally as it happens and send HMRC a quarterly summary, then finalise the year. For a trade where receipts go missing and CIS statements pile up, capturing everything continuously is a genuine improvement. Our guide to MTD for sole traders walks through the quarterly rhythm.
Common Mistakes Decking Installers Make
Not registering for CIS as a subcontractor. Unverified subcontractors lose 30% instead of 20%, tying up more cash until the refund.
Losing CIS deduction statements. Without them you cannot prove the tax already paid, so you cannot reclaim it.
Letting contractors deduct CIS from materials. Always itemise materials separately so the 20% only hits labour.
Mixing van methods. You cannot claim mileage and actual running costs for the same van; pick one and stick to it.
Forgetting direct-to-homeowner income. A deck built straight for a household has no CIS taken, but it is still taxable and must go on your return.
People also ask
Quarterly expenses under MTD: the £90,000 rule
If your annual business turnover is £90,000 or less, HMRC lets you report a single consolidated expenses total in each Making Tax Digital quarterly update instead of breaking expenses down into itemised categories. Most self-employed decking installer businesses are under this threshold, so a quarterly update can be as simple as two figures: total income and total expenses. You still need to keep digital records of each individual expense - the relaxation only changes how much detail goes into the quarterly update itself.
Frequently asked questions
Calculators for decking installers
Helpful guides
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