CIS deductions and refunds, allowable tools, PPE and travel costs, National Insurance, VAT reverse charge and MTD explained for self-employed steel erectors.
Steel erection is hard, high, and unforgiving work, and the tax that sits behind it is shaped almost entirely by one thing: the Construction Industry Scheme. As a self-employed steel erector you rarely get paid your full labour rate. The principal contractor takes 20% off the top before the money reaches you, hands you a deduction statement, and pays HMRC on your behalf. That single mechanic is why steel erectors, like most CIS subcontractors, usually end the year owed money by HMRC rather than owing it.
This guide is built around how steel erectors actually earn and spend: CIS deductions and the refund that follows, the substantial tool, PPE and travel costs that bring your profit down, how National Insurance stacks on top, the VAT domestic reverse charge that governs your invoices, and what Making Tax Digital changes from 2026. Get the record-keeping right on site and the refund follows automatically.
As a sole trader you pay Income Tax on profit, which is your total construction income minus allowable expenses, not on the gross figure on your invoices. 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 settled through Self Assessment.
The twist for a steel erector is that 20% has already been taken from your labour under CIS before you ever see the cash. That deduction is a payment on account of your tax, not a final tax, so at Self Assessment you work out your real liability on profit, then subtract the CIS already deducted. Because the 20% was taken off your gross pay with no credit for your personal allowance, tools or travel, it nearly always overshoots, and HMRC repays the difference.
Scottish steel erectors pay Scottish Income Tax through six bands (19%, 20%, 21%, 42%, 45% and a 48% top rate) on an S-prefixed tax code, while National Insurance stays UK-wide. Welsh erectors have a C-coded tax code at rates currently matching the rest of the UK. If a part-time PAYE job or an old employment is distorting your code, run it through the tax code checker.
The Construction Industry Scheme is the single most important thing to understand as a steel erector, and we cover it in full depth in our guide to CIS subcontractors.
In practice the flow looks like this. You agree a labour rate with the principal contractor or steel fabricator. They verify your CIS status with HMRC, deduct 20% from your labour, pay you the rest, and give you a monthly payment and deduction statement. You bank that statement. Over a tax year those statements add up to the total CIS deducted from you.
At Self Assessment you report the gross figure (labour before the 20% was taken), deduct your allowable expenses to reach profit, calculate Income Tax and Class 4 NIC on that profit, then offset the total CIS deducted. The arithmetic usually lands on a repayment because the flat 20% ignored your personal allowance and every tool, harness and mile you paid for. The CIS tax calculator will estimate your likely refund from your gross income and deductions. Two things protect that refund: register for CIS so the rate is 20% not 30%, and keep every single deduction statement, because they are the evidence HMRC repays against.
This is a high-kit, high-mileage trade, so your expenses are real and substantial, and they are exactly what the 20% CIS deduction failed to account for. Claim actual expenses, not the GBP 1,000 trading allowance, because your genuine costs will dwarf it.
| Expense | What qualifies | Notes |
|---|---|---|
| Tools and equipment | Impact wrenches, spud wrenches, podgers, drills, grinders, slings, shackles, hand tools | Larger purchases claimed via the Annual Investment Allowance |
| Safety and fall-arrest gear | Full-body harnesses, lanyards, fall-arrest blocks, hard hats, work positioning gear | Core PPE for working at height, fully allowable |
| Other PPE | Steel-toe boots, hi-vis, gloves, eye and ear protection, wet-weather gear | Protective clothing and its replacement are allowable |
| Protective clothing cleaning | Laundering hi-vis and work gear, work-only overalls | Everyday clothing is never allowable |
| Vehicle and travel | Van running costs or 45p/25p mileage, fuel, parking, congestion and tolls | Site-to-site travel allowable; ordinary commuting is not |
| Insurance | Public liability and tool insurance | Standard for a self-employed erector |
| Certifications | CSCS card, CPCS/NPORS renewals, IPAF, medicals | Renewing existing tickets is allowable |
| Training and CPD | Refresher courses updating existing skills | Training into a brand-new trade is not allowable |
| Plant and consumables | Bolts, fixings, small tool hire, abrasives, marker spray | Materials reimbursed by the contractor are reported separately |
| Admin | Accountancy, business banking, phone and a share of home-office paperwork costs | Deduct the business proportion only |
Steel erection is one of the most PPE-heavy trades in construction, and that is good news at tax time. Harnesses, lanyards, fall-arrest blocks, work-positioning belts, hard hats with chin straps, steel-toe boots, hi-vis, impact gloves and eye protection are all wholly-and-exclusively business costs, fully allowable, including replacements when gear is damaged or condemned. The cleaning of work-only clothing is allowable too. The line HMRC draws is dual-use everyday clothing: a normal pair of jeans or a fleece you also wear off-site is not deductible even if you wear it to work.
Most erectors run a van and travel between fabrication yards and sites. You can claim actual running costs (fuel, insurance, servicing, repairs, tax) apportioned for any private use, or use HMRC's simplified mileage rate of 45p per mile for the first 10,000 business miles and 25p after that. Pick one method per vehicle and stick with it. Travel to a temporary site is allowable; an ordinary daily commute to a regular workplace is not, and parking, tolls and congestion charges incurred for work follow the same logic.
Steel erectors lose money at tax time through poor records, not poor work. Three habits fix it. First, file every CIS payment and deduction statement the moment it lands, because these drive your refund. Second, photograph and log receipts for tools, PPE and fuel as you buy them, ideally straight into an app, so a GBP 90 pair of boots or a GBP 200 harness is never forgotten. Third, log business mileage trip by trip rather than guessing in January. Capture it as it happens and the annual return becomes a formality.
For a steel erector, the refund is already sitting in your CIS statements. Keep every statement, log every tool and every mile, and Self Assessment turns a year of 20% deductions back into cash.
Take a CIS-registered steel erector with GBP 45,000 of gross labour income for the year, all under CIS, so GBP 9,000 has already been deducted at 20%.
Gross CIS income: GBP 45,000 (CIS deducted at 20% = GBP 9,000)
Allowable expenses:
Taxable profit: GBP 45,000 minus GBP 9,800 = GBP 35,200
Income Tax: GBP 35,200 minus GBP 12,570 = GBP 22,630 at 20% = GBP 4,526
Class 4 NIC: GBP 22,630 at 6% = GBP 1,358
Total Income Tax and NIC: GBP 5,884
CIS already deducted: GBP 9,000
Refund due: GBP 9,000 minus GBP 5,884 = GBP 3,116 back from HMRC.
The refund exists because the flat 20% ignored both the personal allowance and nearly GBP 10,000 of genuine tool, PPE and van costs. Run your own gross income and deductions through the CIS tax calculator or the sole trader tax calculator to estimate your position before you file.
You must register for VAT once taxable turnover passes GBP 90,000 in any rolling 12-month period. For steel erectors there is an extra rule that catches almost everyone working in the supply chain: the construction domestic reverse charge. When you carry out CIS-covered construction work for another VAT-registered, CIS-registered contractor, you do not add VAT to that invoice. Instead you mark it "reverse charge" and the contractor accounts for the VAT to HMRC. You still reclaim VAT on your own tools, van, fuel and PPE, which is why many erectors over the threshold end up in repayment positions on their VAT returns too.
The reverse charge does not apply when you invoice an end client directly, for example a homeowner or a final customer who is not passing the work on, in which case normal VAT rules apply. If most of your work is sub-contracted to fabricators and main contractors, expect the reverse charge to govern the bulk of your invoices.
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 for a CIS subcontractor that means gross before the 20% deduction:
The common trap is testing yourself against the net cash you actually received after CIS. HMRC looks at the gross figure on your CIS statements, so a steel erector banking comfortably under the threshold in net terms can still be over it on gross. Once in MTD you record each payment, tool, PPE purchase and mileage trip digitally as it happens and send HMRC a summary every quarter. For a trade with steady CIS statements and clear receipts, the quarterly rhythm is far less painful than a January scramble. Our guide to MTD for sole traders walks through what the quarterly cycle looks like in practice.
Losing CIS deduction statements. They are the proof of the 20% already taken and the basis of your refund. Lose them and you risk being unable to reclaim what is rightfully yours.
Reporting net income instead of gross. You report the gross labour and claim the CIS deducted separately. Reporting net understates your income and breaks the refund calculation.
Not registering for CIS. Unregistered subcontractors suffer a 30% deduction instead of 20%, tying up more cash until you reconcile at year end.
Claiming the GBP 1,000 trading allowance instead of real costs. With thousands in tools, PPE and van costs, actual expenses always beat the flat allowance for a steel erector.
Getting the VAT reverse charge wrong. Adding VAT to a reverse-charge invoice, or omitting it on a direct end-client job, both cause problems. Know who you are billing and on what basis.
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