Is CIS the same as PAYE?

No. CIS is a deduction towards your self-employed tax. You still file a return. PAYE is employment.

Do I declare the full invoice or what hit the bank?

The full invoice as turnover. Claim CIS as tax already paid.

Yes, either simplified mileage or actual running costs, not both for the same vehicle.

Are materials allowable?

Yes when they are for jobs. If you recharge them, also include the recharge in turnover.

What if CIS is more than my tax bill?

You should get the extra back after you file, if the statements are correct and on the return.

Self-employed plumber tax UK (2026/27)

Expenses list · Self Assessment · Tax calculator · Deadlines

Who this is for

Sole-trader plumbers: domestic call-outs, subcontracting on sites, or a mix. Also gas engineers who invoice as themselves.

If you are on a company’s PAYE, that is employment. If a contractor pays your invoice and withholds CIS, you are still self-employed. Limited company plumbers have a different tax stack (and CIS still exists). This page is the sole trader.

What is the same for every sole trader

If you work for yourself you register with HMRC, keep a record of what came in and what you spent to earn it, and file a Self Assessment return. Tax is on profit, not turnover. The 2026/27 personal allowance is £12,570. Class 4 National Insurance is 6% between £12,570 and £50,270, then 2% above that. The online filing and payment deadline for the 2025/26 return is 31 January 2027.

What is different if you are a plumber

CIS is the plumbing and building trade’s own trap. The contractor deducts a percentage (often 20% if you are registered, 30% if not) from the labour element of your invoice. That money goes to HMRC as a payment on account of your tax. It is not your expense. On the return you declare the full invoice and claim the CIS deducted as tax already paid. Miss the statements and you pay twice.

Materials you buy and recharge to the customer are usually turnover when billed and purchases when bought. Mark-up is profit. Tools stay yours and are equipment, not materials.

The van is both a workplace and a commute machine. Travel from home to a changing list of jobs is usually business. Travel from home to a yard you attend every morning can look like commuting. Keep a log that matches the diary.

Worked example

A plumber invoices £62,000. Materials £9,500. Van (simplified mileage 9,000 miles at 55p) £4,950. Tools £1,800. Insurance £1,100. Phone and software £420. PPE £280. Accountant £550. Public liability already in insurance. Other consumables £1,800. Total expenses £21,400. Separately, CIS of £6,400 was deducted. That £6,400 reduces tax due; it is not in the expense total.

Typical year	Amount
Turnover	£62,000
Materials	£9,500
Van mileage	£4,950
Consumables	£1,800
Tools	£1,800
Insurance	£1,100
Accountant	£550
Phone and software	£420
PPE	£280
Total expenses	£21,400
Taxable profit	£40,600
Income Tax	£5,606
Class 4 NI	£1,681.80
Estimated bill	£7,287.80

Figures use 2026/27 England, Wales and Northern Ireland rates, full personal allowance, no other income. Scotland uses different bands. Run the calculator with your own numbers.

Domestic and some CIS site work, England. CIS deducted is tax paid, not in the £21,400.

Making Tax Digital

Gross invoices can clear £50,000 quickly even when CIS and materials eat the profit. If you were over the MTD line, quarterly digital updates applied from April 2026. CIS does not take you out of MTD.

See does Making Tax Digital apply to me? and the sole trader MTD guide.

Next steps

Related trades

Electrician tax: CIS, test kit, NICEIC-type memberships, van, and certificates as part of the job.
Cleaner tax: Cash houses, mileage between jobs, products, and why “I only do a few hours” still counts.
Freelancer tax: Invoices, platform fees, home office, and MTD if your gross income is already over the line.