One of the big advantages of CIS self-employment over umbrella PAYE is that you can claim business expenses. Those deductions lower your taxable income, which means less tax to pay at year end. HMRC’s rules are still strict, though. Not everything is claimable, and getting it wrong can create a compliance problem. This guide explains what you can claim, and what you can’t.
How do CIS expense claims work?
CIS subcontractors are self-employed. They claim allowable expenses through their self-assessment tax return. Those expenses reduce gross income to arrive at a net profit figure. Tax is calculated on the net profit, not the gross.
Unlike PAYE employment, self-employed workers pay their own business costs. HMRC allows deductions for costs that are “wholly and exclusively” incurred for business purposes. The rules are tighter than many contractors expect.
HMRC does not check every expense claim up front. But it can review past returns and ask for receipts at any time. Keep records for at least five years from the January 31 filing deadline.
Travel and transport expenses
Travel to different construction sites is usually claimable as a business expense. This includes fuel costs, mileage, parking, train fares, and bus fares. The key point is simple: travel between sites is claimable. Ordinary commuting to the same fixed location every day is not.
HMRC decides this by looking at whether a location is your “regular place of work.” If you’re on a short contract at one site for a few weeks and then move on to another site, travel to each site is claimable. If you go to the same site every day for a year, that site starts to look like a regular workplace, and the commuting rules apply.
HMRC’s guidance on temporary workplaces matters here. A workplace is “temporary” if your contract is expected to last 24 months or less, and it does not become your regular workplace before the end of that period.
Mileage rates for 2026-27: 45p per mile for the first 10,000 business miles, 25p per mile after that (using HMRC’s approved mileage rates for self-employed workers).
Tools and equipment
Tools you buy specifically for work are claimable. Small tools, usually under £500 or so, can normally be claimed as revenue expenses in the year you buy them. Larger equipment — vans, plant hire, machinery — may need to be claimed through capital allowances instead.
Examples of claimable tools include hand tools, power tools, and specialist equipment you own rather than hire. You must use them for work. If a tool has both personal and business use, you can only claim the business part.
If your tools are stolen on site, the loss may be claimable — but you’ll need the police reference number and proof of the original purchase.
Protective clothing and workwear
Specialist protective clothing required for construction work is claimable. That includes hard hats, steel-capped boots, hi-vis vests, and safety gloves. Ordinary clothing — even if you only wear it for work — is not claimable unless it is clearly protective gear.
HMRC’s rule is straightforward: functional protective clothing with a clear safety purpose qualifies. General work clothes that could also be worn socially do not qualify, even if you only bought them for work.
If your employer or client provides protective clothing, do not double-claim the same items.
Materials
Materials you supply as part of your work are claimable, but they need careful handling. Materials you invoice for are already excluded from the CIS deduction calculation because the contractor does not deduct CIS on materials. Even so, they still need to be claimed correctly as a business expense on self-assessment.
The materials cost reduces your net profit in the same way as any other expense. But the materials figure on your CIS statements should match your receipts. Keep supplier invoices for everything.
Training and professional development
Training that maintains or updates skills for your current trade is claimable. Training to move into a different trade is not claimable — HMRC treats that as personal development, not a business expense.
For example, a scaffolder attending updated working-at-heights certification is maintaining current skills, so that is claimable. A scaffolder taking a course to become a plumber is changing career, so that is not claimable.
Professional memberships related to your trade are also claimable.
Phone and internet
If you use a phone for business — arranging work, contacting contractors, site management — the business share of the cost is claimable. If the phone is used for both personal and business use, you can only claim the business percentage.
Keep records of how you use the phone. A call log, or a sensible estimate of business versus personal use, helps if HMRC asks.
How do you claim expenses?
You enter claimable expenses on your self-assessment return under “self-employment expenses.” They reduce your taxable profit. Always keep receipts — HMRC can ask for evidence going back five years from the 31 January filing date.
See self-assessment for CIS subcontractors for the full self-assessment filing process, including where expenses go on the return.
What about umbrella PAYE and expenses?
Umbrella contractors face much stricter expense rules. The SDC test means most cannot claim travel and subsistence to their regular workplace. A compliant umbrella company still processes legitimate expenses correctly, but the range of claimable costs is much narrower than for CIS self-employment.
This is one reason CIS subcontractors with higher tool and travel costs often end up ahead on take-home pay compared with umbrella PAYE.
