How do I sign up for Making Tax Digital for Income Tax as a plumber?

Add plumbing turnover before CIS deductions to other self-employed or rental income. Over £30,000 in 2025-26? Sign up on GOV.UK with your Self Assessment sign-in to start on 6 April 2027, or now if over £50,000 in 2024-25.

Making Tax Digital for Income Tax (MTD) works the same for a self-employed plumber, heating engineer or gas engineer as for any sole trader. The difference is that most plumbers have income from several kinds of customer, and only some of it comes through the Construction Industry Scheme (CIS). This page follows GOV.UK's sign-up, MTD and CIS guidance, checked on 17 October 2026. The general sign-up guide covers the service for everyone.

Add up every kind of job

HMRC tests your qualifying income: your self-employment and property income added together, before expenses. That means every job, whoever paid you and however.

Homeowners are not CIS contractors, CIS 340 says. A business outside construction becomes a "deemed contractor" once its construction spending goes over £3 million in any 12 months. In our reading, most landlords and letting agents are nowhere near that, so they usually pay you in full. On CIS work, HMRC's guide lists installing heating, water supply, drainage, sanitation and gas mains, and installing and repairing kitchens and bathrooms. It excludes the repair, servicing and maintenance of heating, water, drainage and sanitation systems. HMRC's manual says replacing even a central heating boiler is not installing a system, though replacing the whole system is. The CIS guide for plumbers has the full list.

Take a heating engineer under £50,000 in 2024-25. In 2025-26 their CIS statements from two builders show gross payments of £14,000. Boiler swaps, repairs and services for homeowners came to £13,500, jobs for landlords and a letting agent to £3,800, and cash call-outs to £1,200. Qualifying income is £32,500. That is over £30,000, so MTD starts on 6 April 2027.

Wages from a job do not count, so a plumber employed by a heating firm who takes private work at weekends tests only the private turnover. Nor does a partner's share of partnership profit.

HMRC writes if you are over the line, but GOV.UK says checking is still your responsibility.

What the sign-up asks a plumber

You must be registered for Self Assessment and have sent a tax return in the last 2 years. GOV.UK then asks for the following.

You may be asked to prove your identity with a phone app and your current passport or driving licence. Since 13 October 2026 you cannot answer questions instead.

Once you are signed up

Record each job's full amount as income, less any VAT if you leave VAT out of your income. For CIS jobs, that is the gross pay before deductions. In our reading, the turnover in your quarterly updates is the gross figure, the same as on your tax return.

For your MTD tax return, HMRC adds the CIS deductions it holds, and you check them against your statements before you submit. A refund cannot be claimed in an MTD tax return: once you have submitted, you request it through your HMRC online services account, or your agent does through theirs.

What this means for you

If your total turnover, plus any rent, was over £30,000 in 2025-26 but not over £50,000 in 2024-25, you sign up for 2027-28 and your first quarterly update is due by 7 August 2027. GOV.UK lets you sign up for the current or the next tax year. Volunteers agree that the new penalties apply, and HMRC confirms when they start. The break from penalty points for late quarterly updates covers 2026-27. The 28 October 2026 Budget said April 2027 joiners get none for 2027-28 updates either, though updates must still be sent, so the earliest possible point is 7 August 2028. After that, each missed deadline earns a point if you must use MTD, not while volunteering, and 4 points means a £200 penalty.

An agent can sign you up instead, once you have authorised them through their HMRC agent services account. They need your full name, date of birth and National Insurance number, plus the business details above. Only your main agent can submit your tax return.

Steps to sign up as a plumber

1. Add up your 2025-26 turnover: gross pay from your CIS statements, homeowner and landlord invoices, and cash jobs, plus any rent or other trade. If you started trading or letting part-way through the year, scale that up to 12 months: HMRC doubles 6 months' trading, and you must scale rent yourself. Put the full-year figure into the free MTD check.
2. Check you are registered for Self Assessment and have filed a return in the last 2 years.
3. Choose MTD software that keeps CIS and non-CIS income apart, or someone to do it for you.
4. Have your business name, address, trade and any recent start date to hand.
5. Sign in to the GOV.UK sign-up service with your Self Assessment user ID and password, add every trade and property, and pick your start year.
6. Complete any identity check, or authorise your agent and let them sign you up.
7. Keep every monthly CIS statement and a record of each cash job.

The trades section has more guides for plumbers and heating engineers.