CIS deductions and refunds, allowable tools and PPE, van and travel costs, NIC, VAT reverse charge and MTD for Income Tax explained for self-employed formworkers.
Formwork is heavy, skilled, capital-intensive work. You build and strike the timber, plywood and steel shuttering that gives wet concrete its shape, set props and clamps, read drawings, and move from site to site with a van full of tools. From a tax point of view that profile matters: high tool spend, real travel costs, and almost always the Construction Industry Scheme sitting over everything. Get those three things right and the annual return usually ends in a refund.
This guide is for the self-employed formworker and shuttering carpenter working as a sole trader or CIS subcontractor. It covers how your profit is taxed, why CIS deductions usually mean money back, the specific tools, PPE and vehicle costs you can claim, record-keeping that survives an HMRC check, National Insurance, the VAT reverse charge that trips up so many trades, and when Making Tax Digital lands for you.
As a sole trader you pay Income Tax on profit, which is your total construction income minus allowable expenses, not on the cash that hits your account. For 2025/26 the personal allowance covers the first GBP 12,570, then you pay 20% up 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 runs at 6% on profit between GBP 12,570 and GBP 50,270 and 2% above, while Class 2 NIC is settled through Self Assessment and protects your State Pension record.
Scottish formworkers pay Scottish Income Tax through six bands (19%, 20%, 21%, 42%, 45% and a 48% top rate) and carry an S-prefixed tax code; Welsh formworkers have a C-coded tax code at rates currently matching the rest of the UK. National Insurance is UK-wide regardless. If you also have a PAYE job, perhaps some employed site work, your tax code controls how your personal allowance is split, so if it looks wrong, run it through the tax code checker.
Almost all formwork is done under the Construction Industry Scheme. The contractor who pays you is required to deduct tax from the labour element of your invoice before paying you, and hand it to HMRC. If you have registered as a CIS subcontractor the rate is 20%; if you have not registered it jumps to 30%, so registering is the first thing to do.
The crucial point is what that 20% is calculated on. It comes off your gross labour with no recognition of your personal allowance and no deduction for your tools, van, fuel or PPE. In effect HMRC is collecting 20% of your turnover as an advance payment. But you are only ever taxed on profit after expenses, and the first GBP 12,570 is tax-free. So when you file Self Assessment and bring in your real costs, the tax actually due is almost always less than what was deducted across the year. The overpayment comes back as a refund.
A worked feel for it: a formworker invoices GBP 45,000 of labour over the year, has GBP 9,000 of allowable costs, leaving GBP 36,000 profit. Income Tax and Class 4 NIC on that profit might come to around GBP 6,500. But 20% of the GBP 45,000 labour, roughly GBP 9,000, was already deducted under CIS. The result is a refund of about GBP 2,500. Run your own figures through the CIS tax calculator to estimate yours, and read the deeper walkthrough on the CIS subcontractor page.
CIS deductions only apply to the labour part of what you charge, not to materials you supply. If you invoice for shuttering ply, timber, fixings or hired props alongside your labour, separate the materials on the invoice so the contractor only deducts tax from the labour. Mixing them up means tax is withheld on materials that should never have been deducted, which inflates the refund you then have to chase. Clean, itemised invoices keep the CIS sums correct from the start.
An expense is allowable when incurred wholly and exclusively for the business. For a formworker the list is dominated by tools, protective gear and travel between sites, which is exactly what makes the refund worthwhile.
| Expense | What qualifies | Notes |
|---|---|---|
| Hand and power tools | Saws, drills, nail guns, levels, hammers, pry bars, clamps and adjustable props | Larger items claimed via the Annual Investment Allowance |
| Consumables | Blades, drill bits, screws, nails, form-release oil, sealant, abrasives | Fully deductible as used |
| Shuttering and formwork kit | Plywood, timber, ties, panel hire, prop hire where you supply them | Deduct as materials or hire cost |
| PPE | Hard hat, steel-toe boots, gloves, hi-vis, goggles, ear and knee protection, dust masks | Protective clothing is fully allowable |
| Vehicle | Van running costs (fuel, insurance, tax, repairs, finance) or simplified mileage | Choose one method and stick to it for the vehicle |
| Travel | Mileage or public transport to temporary sites, parking, congestion charge | Ordinary commuting to one permanent workplace is not allowable |
| Tool insurance and storage | Cover for theft from van or site, lock-up rental | Deductible where solely for work |
| Phone and admin | Business share of mobile, a flat-rate home-working allowance for paperwork | Apportion private use out |
| Certification | CSCS card, ticket renewals, plant or scaffold tickets, first aid | Maintaining tickets you already hold is allowable |
| Training | Courses that update existing formwork or H&S skills | Training into a brand-new trade is not allowable |
| Subscriptions and fees | Trade body membership, accountancy, business banking | Fully deductible |
Tools are the formworker's biggest deduction. Small consumables and hand tools are written off in full as everyday expenses. Bigger purchases, a quality circular saw, a nail gun, a set of adjustable steel props, are capital but can almost always be claimed in full in the year you buy them under the Annual Investment Allowance, so the whole cost comes off your profit. Keep the receipts; HMRC can ask to see them, and a stolen-tools insurance claim will too.
Most formworkers run a van between sites. You can claim actual running costs (fuel, insurance, road tax, servicing, repairs and finance interest, scaled for private use) or HMRC's simplified flat mileage rate of 45p per mile for the first 10,000 business miles and 25p thereafter. The flat rate is simpler and needs only a mileage log; actual costs can be larger for a thirsty older van with heavy repair bills. Travel to a series of temporary sites is allowable, but if you attend the same site every day for a long contract HMRC may treat it as a permanent workplace, and ordinary commuting is never allowable. The sole trader tax calculator shows how different expense totals move your profit and refund.
Everyday clothing is not allowable even if you only wear it for work; only genuine protective gear counts. The private share of your van, phone and any dual-use kit must be excluded. Meals on an ordinary working day are not deductible, and neither are fines or parking penalties. Materials you bill straight on to a contractor are their cost in effect, so do not double-count them as your expense while also recovering them on the invoice.
For a formworker the refund is built from receipts. Every blade, prop, litre of fuel and pair of boots you log brings the taxable profit down and the repayment up. The tools you forget to claim are money left with HMRC.
Formwork is messy for paperwork: cash for sundries, card for fuel, paper CIS statements and invoices to several contractors. Keep it continuous. Photograph every receipt the day you get it, keep all CIS deduction statements together, log van mileage as you go, and record each invoice gross before any CIS deduction. Filing CIS statements as they arrive is the most valuable habit, because they are your proof of tax already paid and your route to the refund.
Two classes apply. Class 4 NIC is 6% on profit between GBP 12,570 and GBP 50,270 and 2% above, calculated automatically within Self Assessment. Class 2 NIC is also collected through Self Assessment and is what builds your entitlement to the State Pension and certain benefits; if your profit is low you can pay it voluntarily to protect your record. Because CIS only deducts Income Tax and not NIC, your Self Assessment still has to settle the Class 4 due, which is why the refund is the net of overpaid tax against the NIC owed.
You must register for VAT once taxable turnover passes GBP 90,000 in any rolling 12-month period. Plenty of busy formworkers reach this on labour and materials combined. Once registered, most construction work you do for other VAT-registered businesses falls under the domestic reverse charge for building and construction services. In practice that means you do not add VAT to your invoice to the contractor; they account for the VAT to HMRC themselves. You still reclaim VAT on your own tools, van, fuel and materials, which can put you in a regular repayment position. Your invoice must state that the reverse charge applies and show the rate that would otherwise have been charged. Getting this wrong, charging VAT when the reverse charge applies, is one of the most common construction VAT errors.
Making Tax Digital for Income Tax replaces the once-a-year return with quarterly digital submissions and a year-end finalisation. The thresholds are based on gross income before expenses and before CIS deductions:
The catch for CIS workers is that the test is on gross turnover, the labour figure on your invoices, not the smaller amount that reaches your bank after 20% is taken. A formworker invoicing GBP 55,000 of labour is in scope from April 2026 even though perhaps GBP 44,000 actually landed. Under MTD you keep digital records and send HMRC a summary each quarter using compatible software, then finalise the year. The upside is that CIS statements, tool receipts and mileage captured continuously make the quarterly rhythm far easier than a year-end scramble. Our guide to MTD for sole traders walks through what the quarters look like in practice.
Not registering for CIS. Unregistered subcontractors are deducted at 30% instead of 20%, tying up even more cash until the refund. Register before you start invoicing.
Losing CIS statements. No statement, no proof of tax paid, no refund. They are the single most important document you handle.
Letting tax be deducted on materials. Separate materials from labour on every invoice so CIS only hits the labour element.
Forgetting van and tool insurance costs. Big tool spend is obvious; the mileage log, parking and theft cover get missed and they add up.
Charging VAT when the reverse charge applies. Once VAT-registered, most contractor work is reverse-charged, so adding VAT is an error you will have to correct.
Tax guide for Vinted sellers in the UK: trading vs selling personal items, the GBP 1,000 trading allowance, allowable expenses, the platform data HMRC now receives, VAT and MTD.
UK Airbnb tax guide: the GBP 7,500 Rent a Room scheme, the GBP 1,000 property allowance, the abolition of furnished holiday lettings, allowable expenses, VAT and MTD for landlords.
The complete UK tax guide for Uber drivers: gross fares, mileage claims, Uber service fees, VAT, and what MTD for Income Tax means for you.
UK eBay seller tax guide: selling personal items vs trading, the GBP 1,000 trading allowance, eBay fees, the platform reporting rules, VAT and MTD.
Tax guide for self-employed hairdressers: chair rent, allowable expenses, mileage, VAT and MTD for Income Tax explained in plain English.
Everything self-employed taxi and private-hire drivers need to know about tax, mileage vs actual costs, VAT, and Making Tax Digital in 2025/26.
TapTax connects to your bank, categorises expenses automatically, and submits quarterly updates to HMRC. Free plan, no card required.
