CIS allowable expenses: the complete guide
Tax year 2026/27 · Reviewed July 2026
Every legitimate expense you claim reduces your taxable profit — and because CIS tax has already been deducted from your gross pay, every pound of expenses feeds almost directly into a bigger refund. Most under-claimed refunds we see aren't caused by maths errors; they're caused by expenses nobody told the subcontractor they could claim.
The golden rule from HMRC is that costs must be incurred "wholly and exclusively" for your trade. Where something is mixed business/personal (a phone, a vehicle), you claim the business share.
Tools, equipment and materials
- Hand and power tools — purchase, repair, replacement and hire.
- Materials you buy yourself for jobs (where the contractor doesn't supply or reimburse them).
- Consumables — blades, fixings, sealant, sandpaper, gas bottles.
- Larger equipment (mixers, scaffolding, generators) — usually claimable in full in the year of purchase via the Annual Investment Allowance.
Protective clothing and PPE
- Safety boots, hard hats, hi-vis vests and jackets, gloves, goggles, ear defenders, knee pads.
- Ordinary clothes (jeans, trainers) are not claimable, even if you only wear them for work — the test is protection or uniform, not habit.
Vehicle and travel
- Simplified mileage: 45p per mile for the first 10,000 business miles each year, 25p after that — covers fuel, insurance, repairs and depreciation in one figure. Easiest if you keep a mileage log.
- Or actual costs: the business share of fuel, insurance, servicing, repairs, MOT and finance interest — usually better for vans in heavy use. You pick one method per vehicle and stick with it.
- Parking and tolls while working (parking fines are never allowable).
- Public transport to sites, and reasonable accommodation and subsistence when working away overnight.
- Ordinary commuting to a single permanent workplace isn't claimable — but most subcontractors moving site to site are travelling to temporary workplaces, which is.
Insurance, phone and admin
- Public liability insurance and tool insurance.
- Mobile phone and internet — the work-use percentage.
- Accountancy and bookkeeping fees (including fees for claiming your refund).
- Bank charges and interest on a business account.
- Stationery, printing, software and job-quoting apps.
- A flat working-from-home allowance for doing your quotes, invoices and paperwork.
Training and subscriptions
- CSCS card renewals, safety tickets (CPCS, SMSTS, IPAF and similar) and courses that update or maintain existing skills.
- Union subs and trade body memberships.
- Training for a completely new trade is treated as capital and generally not allowable — worth a conversation before you assume either way.
What you can't claim
- Everyday clothing, lunches on a normal working day near home, commuting to one fixed workplace.
- Fines and penalties (parking, speeding, late filing).
- Client entertaining.
- The personal share of any mixed-use cost.
Records: what to keep
Keep receipts, invoices, bank statements and a mileage log for at least 5 years after the 31 January filing deadline for each return. Photos of receipts on your phone are fine. No receipt isn't automatically fatal — a bank statement entry plus a credible explanation often suffices — but paper beats memory every time HMRC asks questions.
What's it all worth?
As a rule of thumb at the 20% basic rate, every £1,000 of legitimate expenses adds roughly £260 to your refund (£200 income tax + £60 Class 4 National Insurance, within the main bands). A subcontractor with a van, tools and insurance can easily have £5,000–£8,000 of allowable costs — try your own numbers in our refund calculator.
Get my expenses checked & claim my refund
This guide is general information for self-employed CIS subcontractors (sole traders), not advice for your specific circumstances. Rules differ for limited companies. See our terms & disclaimer.