CIS deductions and refunds, allowable tools, van and PPE costs, record-keeping, VAT and MTD for Income Tax explained for self-employed UK glaziers.
For a self-employed glazier the tax picture is shaped by two things: a vehicle full of expensive kit, and the Construction Industry Scheme quietly skimming 20% off your labour on every contractor invoice. Get both right and you usually finish the year owed money by HMRC rather than owing it. Get them wrong and you either overpay through unclaimed CIS deductions or under-record the materials and tools that should be cutting your bill.
Whether you are replacing a smashed shopfront on a high street, fitting double-glazed units in a new-build, installing curtain walling on a commercial job, or doing emergency board-ups, the money tends to arrive net of CIS, with materials flowing through your books and a constant trickle of spend on blades, sealant and fuel. This guide is built around how a glazier actually earns and spends, so the annual return becomes a reconciliation rather than a scramble.
As a sole trader you pay Income Tax on your profit, which is your total glazing income minus allowable expenses, not on the gross amount a contractor pays you. 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 glaziers 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 glaziers have a C-coded tax code at rates currently matching the rest of the UK. If you also do PAYE work for a fabricator or installer and your code looks wrong, run it through the tax code checker so you are not taxed twice on the same allowance.
If you install glazing as part of construction or building work for a contractor, you almost certainly fall inside the Construction Industry Scheme. Fitting windows, glazed units, shopfronts, curtain walling, partitions and structural glass for a contractor counts as construction operations. The contractor must deduct money from the labour element of your invoice and pay it to HMRC on account of your tax.
Two practical points decide how much CIS costs you up front. First, register as a CIS subcontractor so the rate is 20%, not 30%. Second, split labour and materials clearly on every invoice, because the deduction only applies to labour. If you bill GBP 2,000 labour plus GBP 1,500 for the glazing units, the deduction is 20% of GBP 2,000, not the whole GBP 3,500. Our full CIS subcontractor guide walks through registration, gross payment status and the statements you must keep.
The 20% deduction is a blunt instrument. It takes no account of your personal allowance, your van, your tools, your insurance or your materials. Once you deduct genuine business costs and apply the GBP 12,570 personal allowance, your real tax bill on profit is frequently lower than the CIS already taken. At Self Assessment the deductions are credited against your Income Tax and Class 4 NIC, and the excess comes back to you. The CIS tax calculator shows the likely refund once your deductions and expenses are entered.
The one rule that protects this refund: keep every CIS payment and deduction statement from each contractor. Without them you cannot evidence what was withheld, and you risk losing the credit you are owed.
An expense is allowable when incurred wholly and exclusively for the business. Glazing is equipment and vehicle heavy, so this list matters more than for most trades.
| Expense | What qualifies | Notes |
|---|---|---|
| Hand and power tools | Suction-cup lifters, glass cutters, beading and putty knives, cordless drills, sealant guns | Often claimed in full via the Annual Investment Allowance |
| Access equipment | Ladders, step-ups, scaffold towers, glass-handling trolleys | Larger items go through capital allowances |
| Van and vehicle | Purchase via capital allowances, plus running costs | Choose simplified mileage or actual cost, not both |
| Fuel and mileage | Diesel, or 45p per mile for the first 10,000 business miles then 25p | Commuting to a regular site is not allowable |
| Materials | Glazing units, sealant, beading, fixings, packers, putty | Deductible; on CIS jobs list these separately from labour |
| PPE and workwear | Cut-resistant gloves, safety boots, goggles, hard hat, logo workwear | Everyday clothing is never allowable |
| Insurance | Public liability, tool and van insurance, professional indemnity | Fully deductible business cover |
| Waste disposal | Removing and tipping broken glass and old frames | Keep tip receipts |
| Phone and admin | Business share of mobile, a fair home-office proportion for quoting and invoicing | Exclude the private share |
| Training and tickets | CSCS card, working-at-height and abrasive-wheels courses | Updating existing skills only |
| Accountancy and bank fees | Bookkeeping, Self Assessment, business banking | Fully deductible |
Big purchases such as a van, a scaffold tower or a full set of suction lifters are usually claimed through the Annual Investment Allowance, which lets you deduct the full cost in the year you buy, rather than spreading it. That can wipe out a large chunk of profit in a year you re-equip. For the van you choose one method and stick with it: either simplified mileage at 45p (then 25p over 10,000 miles), or the actual share of fuel, insurance, servicing, road tax and capital allowances on the vehicle. A glazier doing high mileage between sites should run both methods once and keep the larger.
The private share of a dual-use phone, van or fuel must be excluded. Everyday clothing is never allowable even if it gets wrecked on site, though branded workwear and genuine PPE are fine. Fines, parking penalties and the cost of your own driving licence are out. And ordinary commuting from home to a site you attend regularly is not deductible, even though travel between jobs during the day is.
Take a CIS-registered glazier doing mostly commercial shopfront and replacement work for contractors, with GBP 46,000 of labour and materials billed for the year and GBP 6,400 of CIS already deducted from labour.
Turnover: GBP 46,000 (labour GBP 32,000, materials GBP 14,000)
Allowable expenses:
Taxable profit: GBP 46,000 minus GBP 18,200 = GBP 27,800
Income Tax: GBP 27,800 minus GBP 12,570 = GBP 15,230 at 20% = GBP 3,046
Class 4 NIC: GBP 15,230 at 6% = GBP 914
Tax and NIC due: GBP 3,960. But GBP 6,400 of CIS has already been deducted, so the glazier is owed a refund of roughly GBP 2,440. Run your own labour, materials and CIS figures through the sole trader tax calculator to sanity-check the result before you file.
For a glazier, the CIS statements in the glovebox are worth more than any single invoice. Keep every one, deduct every tool and mile, and the tax year usually ends with HMRC owing you.
Glazing record-keeping fails in the same place every year: receipts for sealant, blades, fixings and fuel that never made it out of the van. Build a habit of photographing each receipt the moment you pay, logging the mileage between jobs, and filing every CIS deduction statement as it arrives. Keep materials and labour separated on your own invoices so CIS is only ever applied to labour. Do this continuously and the annual return is a reconciliation, not an archaeology dig through a shoebox.
You must register for VAT once taxable turnover passes GBP 90,000 in any rolling 12-month period. Busy glaziers fitting commercial shopfronts and curtain walling reach this more often than they expect, especially when materials run through their books. Once registered, most construction services you supply to VAT-registered contractors fall under the domestic reverse charge: you do not add VAT to those invoices, and the contractor accounts for it instead. You must state on the invoice that the reverse charge applies and that the customer accounts for the VAT. Get this wording wrong and you risk charging VAT you should not, or losing it on a job where you should have. Work direct for private householders is normally standard-rated as usual.
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, not profit and not take-home after CIS:
A subtle trap for CIS subcontractors: the threshold uses gross turnover before the 20% deduction, so a glazier taking home well under GBP 50,000 after CIS can still be over the line on turnover. Instead of pulling a year of statements together each January, you record each invoice, material purchase and CIS deduction digitally as it happens and send HMRC a quarterly summary. Our guide to MTD for sole traders shows what the quarterly rhythm looks like on the tools.
Not registering for CIS. Staying unregistered means 30% is deducted instead of 20%, tying up more of your cash with HMRC until you file.
Applying CIS to the whole invoice. The deduction is on labour only. List materials separately so the contractor does not over-deduct.
Losing the deduction statements. No statement, no evidence, no refund. File every one.
Mixing van methods. You cannot claim simplified mileage and actual running costs on the same vehicle in the same year. Pick one.
Judging the MTD threshold on take-home. It is measured on gross turnover before CIS and before expenses, so check your full billed income.
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