How do I submit a quarterly update to HMRC as a plumber?

Your software sends HMRC turnover and cost totals for the year so far, with homeowner and CIS jobs together and card takings before fees. If you start in April 2027, your first update is due by 7 August 2027.

Making Tax Digital for Income Tax (MTD) asks for totals each quarter, not receipts. A plumber's quarter often mixes homeowner jobs paid by card with builder jobs that may sit inside the Construction Industry Scheme (CIS). All of it goes in one update. Checked against GOV.UK and HMRC's CIS manual on 18 October 2026; the general guide covers everyone.

Who sends them, and when

You join when your qualifying income, self-employment and property income before expenses, goes over the line: over £50,000 in 2024-25 meant 6 April 2026, over £30,000 in 2025-26 means 6 April 2027, and over £20,000 in 2026-27 means 6 April 2028. The sign-up guide for plumbers shows how to add up your jobs.

If your accounts run from 1 April to 31 March, GOV.UK says to use calendar periods ending 30 June, 30 September, 31 December and 31 March, with the same deadlines; choose them in your software before your first update of the year. A quarter with no income or expenses still needs an update.

Homeowner jobs and card takings

CIS 340 says householders are not contractors, so a homeowner pays you in full. In our reading, a landlord who only lets property is not one either unless its construction spending passed £3 million in the previous 12 months. A letting agent acting for a landlord generally is not, but can be if it contracts in its own name.

Card readers usually pay out with their fee already taken. GOV.UK says that if you only know your income after expenses, you find the full amount, record it as income and record the expenses separately. HMRC's tax return notes say turnover includes card payments. So a £300 boiler service paid by card is £300 of turnover, and in our reading the fee goes in "bank, credit card and other financial charges". The card fees guide has more.

Jobs for builders: in CIS or not

CIS changes how you are paid, not whether a job goes in the update. HMRC's manual and CIS 340 draw the lines, and the CIS guide for plumbers sorts more jobs:

• In CIS: installing or replacing a whole heating, drainage, sanitation, water or gas supply system, and installing or repairing kitchens and bathrooms.
• Out on their own: repairs, servicing and maintenance, an extra radiator, and a boiler swap, which the manual says is not installing a system even though the boiler is a major part.
• Mixed contracts: making good to the building, or other construction work in the same contract, brings every payment under it into CIS.

HMRC's notes say a subcontractor's turnover is the full amount before CIS deductions. MTD uses the same categories as Self Assessment, so in our reading the gross figure on each monthly payment and deduction statement goes in, not what your bank shows.

Boilers, parts and the van

Contractors do not take the deduction from materials you paid for directly. In our reading, the boilers, pipe and fittings you charge for are turnover, and what you paid at the merchant goes in "cost of goods bought for resale or goods used", which HMRC's notes say includes raw materials. Van fuel, insurance and servicing go in "car, van, and travel expenses", business share only.

The law requires self-employed people doing gas work to belong to a class approved by the Health and Safety Executive, so in our reading your Gas Safe Register fee is a cost of trading for "other business expenses", where HMRC's notes put trade subscriptions. The plumber expenses guide lists more.

With turnover from the trade under £90,000, GOV.UK lets you record each item as just income or an expense. Reach £90,000, and every record for the year must be fully categorised before your next update.

What stays out of the update

HMRC's quarterly update direction lists the totals an update holds, and CIS deductions are not among them. HMRC adds your CIS deductions to your MTD tax return, and any refund is requested separately through HMRC online services, as the CIS refund guide explains.

A worked example

A plumber starts MTD on 6 April 2027. By 5 July 2027 he has fitted a bathroom for a builder: £4,500 labour plus £2,000 for the suite and pipe he bought. The builder takes 20% from the labour only, £900, and pays £2,300 in full for a boiler swap under a separate contract. Homeowners pay £7,200 for services, repairs and boilers, £5,400 by card, and the card provider keeps £90. Other merchant purchases total £3,100, and van costs £640.

His bank received £15,010, but his turnover is £16,000. This is an example only.

What this means for you

A mistake is fixed in your records and carried by the next update. If you must use MTD, a late update can earn a point from 2027-28 (joined April 2026) or 2028-29 (joining April 2027, per the 28 October 2026 Budget); 4 points bring a £200 penalty. Compare MTD software for plumbers, or see who can send updates for you.

Steps to send your update as a plumber

1. Download card provider statements showing takings before fees.
2. Collect builders' statements for deductions taken, and chase any missing.
3. Check each builder job against the CIS lines above, reading the whole contract.
4. Record homeowner and card jobs in full, and CIS payments gross with the deduction noted.
5. Record merchant receipts, van costs, card fees and your Gas Safe fee.
6. Check turnover against your invoices and statements, not your bank.
7. Send the update by the deadline.
8. After the fourth update, check the CIS deductions HMRC adds to your tax return, then submit by 31 January.

The free MTD check shows when you start, and the trades section has more guides on CIS and MTD.