Tax Guide for Plumbers: What You Can Claim in 2025/26

Tax Does Not Have to Be a Drain

If you are a self-employed plumber, you are in good company. Plumbing is one of the most common trades for sole traders in the UK, and that means HMRC knows your industry well. The upside is that there are plenty of legitimate expenses you can claim to reduce your tax bill.

This guide walks you through everything you need to know for the 2025/26 tax year — from the expenses you can claim to how CIS deductions work and whether flat-rate mileage or actual costs give you a better deal.

What Expenses Can Plumbers Claim?

To be claimable, an expense must be wholly and exclusively for your business. If something is partly personal and partly business, you can only claim the business portion.

Tools of the Trade

Claimable tools include pipe cutters, wrenches, spanners, soldering and brazing equipment, pipe bending tools, drain rods, inspection cameras, pressure testing equipment, pipe freezing kits, and radiator keys. Smaller tools can be claimed as a straightforward expense. Bigger items go through capital allowances, though the Annual Investment Allowance of £1 million means you can usually claim the full cost in the year of purchase.

Pipe Stock and Materials

Materials bought for jobs — copper pipe, plastic fittings, solder, flux, PTFE tape, compression fittings, valves, taps, replacement parts, bathroom fittings, boiler parts — are all business expenses. Keep every receipt. If a customer pays a single price that includes materials, record the full amount as income and claim the material cost separately.

Gas Safe Registration

If you work on gas appliances, your Gas Safe registration fee (typically £400-£500) is fully claimable. The old CORGI scheme was replaced by Gas Safe in 2009. Other claimable registrations include CIPHE membership, WaterSafe, OFTEC, and unvented hot water systems qualifications.

Training and CPD

Training that updates or maintains your existing skills is claimable: Gas Safe renewal assessments, unvented hot water qualifications, WRAS training, Legionella awareness, renewable energy courses (heat pumps, solar thermal), first aid, and asbestos awareness. Expanding your plumbing skills — say, from domestic to commercial gas — would normally qualify.

Van Costs

You have two choices. Actual costs — fuel, insurance, road tax, MOT, servicing, repairs, tyres, breakdown cover, and financing costs. If you use the van for personal trips, work out the business percentage and only claim that. Or the flat-rate mileage method — 45p per mile for the first 10,000 business miles, 25p after that. With mileage, you cannot separately claim for fuel, insurance, or repairs.

Generally, if you do high mileage with an older van, the mileage rate works out better. If your van is newer with higher finance payments, actual costs may give a bigger deduction. Whichever you choose, you must stick with that method for the life of that vehicle.

PPE, Workwear, and Insurance

PPE is claimable: safety boots, hi-vis clothing, knee pads, safety goggles, dust masks, hard hats, and gloves. Branded workwear with your business name is claimable; everyday clothing is not. All business insurance is claimable — public liability, professional indemnity, employers' liability, tool insurance, and van insurance (if using actual costs).

Other Claimable Expenses

Phone costs (full if a separate business phone, proportionate if personal), accountancy and bookkeeping fees, software subscriptions, advertising and marketing, trade magazine subscriptions, stationery, and bank charges.

CIS: Does It Apply to You?

The Construction Industry Scheme applies to plumbing work done for contractors in the construction industry. If you do subcontract work for a main contractor — for example, plumbing on a new-build housing site — CIS applies.

The contractor deducts 20% from your payment if you are CIS-registered, or 30% if you are not. These are advance payments of your tax, credited against your bill when you file Self Assessment. If more was deducted than you owe, you get a refund.

Register for CIS if any of your work falls under it — the difference between 20% and 30% deductions significantly affects cash flow. With a clean compliance record, you can apply for gross payment status.

CIS does not apply to work done directly for homeowners. If Mrs Jones calls you to fix her boiler, that is a straightforward self-employment job with no CIS deductions.

Home Office Costs

If you run admin from home — invoicing, ordering materials, taking calls — you can claim a proportion of your household costs. HMRC's simplified flat rate is £10/month for 25-50 hours worked from home, £18 for 51-100 hours, or £26 for 101+ hours. Alternatively, calculate the actual proportion of your household costs that relates to business use.

Keeping Good Records

Keep records of all income and expenses for at least five years: invoices, receipts, bank statements, CIS statements, and mileage logs. The shift to Making Tax Digital makes it worth getting into the habit of recording everything as it happens. Accounted's AI bookkeeper Penny can categorise your expenses automatically, so you are not stuck with a carrier bag of receipts in January.

Ready to Get Your Plumbing Taxes Sorted?

You became a plumber to fix pipes, not to wrestle with tax paperwork. But staying on top of your expenses means keeping more of the money you earn. If you want a simple way to track income, claim every expense you are entitled to, and have your tax return figures ready without the stress, start your free trial with Accounted today. Penny will keep your books in order so you can keep your customers' water flowing.

Related Reading

• Tax Guide for Florists and Floral Designers
• VAT on Property: Residential vs Commercial Rules

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