CIS deductions and refunds, allowable tools, van and PPE expenses, Class 4 NIC, the VAT reverse charge and MTD explained for self-employed steel fixers.
For a self-employed steel fixer, tax is not really about owing HMRC money at the end of the year. It is about getting back the money already taken from you. Every time a contractor pays your labour, they hold back 20% under the Construction Industry Scheme and hand it to HMRC. That deduction is calculated on your gross pay, before any of the tax-free allowance or your tools, van and PPE costs are taken into account. So by the time the tax year ends, the running total of those deductions almost always exceeds what you actually owe, and the job of your Self Assessment return is to claim the difference back.
This guide is built around how steel fixers really earn: bar bending and fixing rebar cages on slabs, columns and decks, paid through CIS by a labour agency or a main contractor, often moving between sites and sometimes between contractors in the same week. Get the CIS statements and the expenses right and the refund follows. Miss them and you leave your own money sitting with HMRC.
As a sole trader you pay Income Tax on profit, which is your total income minus allowable expenses, not on the gross figure your contractor pays. 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. Class 4 National Insurance is 6% on profit between GBP 12,570 and GBP 50,270 and 2% above, with Class 2 NIC now settled through Self Assessment.
Scottish steel fixers pay Scottish Income Tax 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 steel fixers have a C-coded tax code at rates currently matching the rest of the UK. If you also have a PAYE job and your code looks wrong, run it through the tax code checker so your allowance is not being used twice.
The Construction Industry Scheme governs how nearly all steel fixers are paid. When a contractor pays you, they deduct tax from the labour portion of your invoice and pay it to HMRC on your behalf. The full mechanics, registration and refunds are covered in our dedicated CIS subcontractor guide, but the essentials for a steel fixer are these.
Two numbers matter. Register as a CIS subcontractor and you are deducted at 20%; fail to register and the rate jumps to 30%, so registration is the first thing any new steel fixer should do. Either way, the deduction is only an advance. Because it is taken off your gross labour before your GBP 12,570 personal allowance and before any expenses, the amount withheld is almost always more than your final liability. That gap is your refund.
The discipline that secures the refund is paperwork. Every contractor must give you a CIS payment and deduction statement, usually monthly. These statements are the evidence HMRC matches against your return, so keep all of them, check the deducted figures, and chase any that do not arrive. You report your gross income and the total CIS already deducted, and HMRC offsets one against the other.
Take a steel fixer paid GBP 45,000 of labour through CIS over the year, all deducted at 20%.
Gross labour income: GBP 45,000 CIS deducted at 20% during the year: GBP 9,000
Allowable expenses:
Taxable profit: GBP 45,000 minus GBP 6,500 = GBP 38,500
Income Tax: GBP 38,500 minus GBP 12,570 = GBP 25,930 at 20% = GBP 5,186
Class 4 NIC: GBP 25,930 at 6% = GBP 1,556
Total tax and NIC due: GBP 6,742. But GBP 9,000 has already been deducted under CIS, so HMRC owes a refund of GBP 2,258. Run your own figures through the CIS tax calculator to estimate your refund before you file, then cross-check the profit with the sole trader tax calculator.
An expense is allowable when it is incurred wholly and exclusively for the business. For a steel fixer the big-ticket item is usually the vehicle, followed by tools, protective equipment and site consumables.
| Expense | What qualifies | Notes |
|---|---|---|
| Van and vehicle | Running costs, fuel, insurance, road tax, MOT, repairs and servicing | Claim actual costs (business share) or simplified mileage, not both |
| Hand tools | Pliers, nips, cutters, bar benders, tie wire reels, tape, levels | Small tools deductible in the year bought |
| Power tools | Rebar cutters and benders, grinders, drills, batteries | Larger items via the Annual Investment Allowance |
| Consumables | Tying wire, tie clips, spacers and chairs you buy yourself | Deduct if you supply them rather than the contractor |
| PPE | Safety boots, gloves, hard hat, hi-vis, knee pads, eye and ear protection | Genuine protective gear is allowable; ordinary clothing is not |
| Insurance | Public liability and tool/equipment cover | Fully deductible business cover |
| Cards and training | CSCS card, CPCS or NPORS tickets, ticket renewals and refresher courses | Renewing existing qualifications is allowable |
| Phone and admin | Business share of mobile, a home-office admin allowance | Apportion private use out |
| Accountancy | Bookkeeping, Self Assessment and CIS return preparation | Fully deductible |
| Travel and subsistence | Mileage to temporary sites, parking, tolls | Travel between your base and a temporary workplace, not ordinary commuting |
For most steel fixers the van is the single largest deduction, because you carry tools and bar-fixing kit and move between sites. You have a choice each year. The simplified mileage method lets you claim 45p per business mile for the first 10,000 miles and 25p after that, with no need to itemise running costs. Alternatively you claim the actual business proportion of every van cost, fuel, insurance, tax, servicing and repairs, plus capital allowances on the van itself. A high-mileage fixer often does better on actual costs; someone doing modest local miles in a cheap van may do better on the flat rate. Work it out once and use the bigger figure, but you cannot switch methods on the same vehicle mid-life.
Ordinary clothing is never allowable even if you only wear it on site; only genuine protective equipment counts. The private share of your van, fuel and phone must be stripped out. Fines, parking penalties and the cost of getting to a permanent base are not deductible. And meals are only claimable in limited circumstances, typically when working away at a temporary site, not for everyday lunches.
Steel fixers lose money to weak records, not to the taxman. The two things that matter most are your CIS deduction statements and your expense receipts. Keep every monthly statement from every contractor, because if you change site or agency partway through the year you will have statements from several. Photograph tool, fuel and PPE receipts as you buy them, log your business mileage, and keep van and insurance documents together. When the numbers on your return match the statements HMRC holds, the refund is paid quickly; mismatches trigger queries and delay.
A steel fixer's tax return is a refund claim. The money is already gone to HMRC under CIS, and your records are what bring it back. Keep every deduction statement and every receipt and the refund looks after itself.
As a sole trader you pay Class 4 NIC at 6% on profit between GBP 12,570 and GBP 50,270, then 2% on profit above that. Class 2 NIC is now collected through Self Assessment and matters because it protects your entitlement to the State Pension and certain benefits, so make sure it is recorded even in a low-profit year. National Insurance is UK-wide, so Scottish and Welsh steel fixers pay the same Class 4 and Class 2 rates as everyone else, even though their Income Tax differs.
You must register for VAT once your taxable turnover passes GBP 90,000 in any rolling 12-month period. Labour-only steel fixers often stay below this, but if you supply materials as well as labour on larger contracts you can reach it, so watch your rolling turnover rather than the tax year alone.
The twist for construction is the domestic reverse charge. If you are VAT-registered and working for another VAT-registered contractor under CIS, you do not add VAT to your invoice. Instead the contractor accounts for the VAT to HMRC, and your invoice must state that the reverse charge applies. This was brought in to stop VAT fraud in construction, and it means a VAT-registered steel fixer collects less cash up front but still reclaims VAT on tools, the van and other business costs.
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 before CIS deductions and before expenses:
Crucially, the test uses your gross labour figure, not the net amount that lands in your bank after the 20% CIS deduction. A steel fixer earning GBP 45,000 gross is measured on GBP 45,000, even though only GBP 36,000 reaches your account. Under MTD you record income and expenses digitally as you go and send HMRC a quarterly summary, with CIS still flowing through the year and being reconciled at finalisation. Our guide to MTD for sole traders walks through the quarterly rhythm in practice.
Not registering for CIS. Staying unregistered means a 30% deduction instead of 20%, tying up even more of your cash until you file.
Losing CIS statements. Without the monthly deduction statements you cannot prove what was withheld, and your refund stalls.
Forgetting the van is the biggest deduction. Failing to claim mileage or actual van costs leaves a large, legitimate expense on the table and shrinks your refund.
Claiming ordinary clothing. Only genuine PPE is allowable; everyday workwear and casual clothes are not, even if only worn on site.
Assuming the 20% is your final tax. It is an advance. You still file Self Assessment, and most steel fixers are owed money back once allowances and expenses are applied.
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