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

Sign up on GOV.UK with your Self Assessment sign-in. If your turnover before CIS deductions was over £30,000 in 2025-26, you start on 6 April 2027, unless it was over £50,000 in 2024-25: then you should already have started.

Making Tax Digital for Income Tax (MTD) applies to self-employed builders the same way it applies to any sole trader. What is different is how the numbers look when you work under the Construction Industry Scheme (CIS), and what you tell HMRC about your trade. 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.

Do you need to sign up, and for which year

HMRC tests your qualifying income: your self-employment and property income before expenses, also called turnover. For a subcontractor, that is your pay before CIS deductions, not what reaches the bank. The turnover guide explains why.

Wages from a job do not count. Take a builder with a PAYE job paying £28,000 who also does CIS work on the side, under £50,000 in 2024-25. In 2025-26, on labour-only jobs, contractors paid £25,000 into the bank after taking 20%, so the pay before deductions was £25,000 ÷ 0.8 = £31,250. Only the £31,250 is tested. It is over £30,000, so MTD starts on 6 April 2027. Contractors do not take the deduction from materials you have paid for, so if your invoices include materials, add up the gross figures on your monthly statements instead.

HMRC checks your return and writes to you if you are over the line, but GOV.UK says you must check yourself even without a letter. The builders' start dates guide has the full timetable.

What the sign-up asks a builder

You need to be registered for Self Assessment and to have sent a tax return in the last 2 years. Then GOV.UK lists the details below.

GOV.UK says a sole trader with different trades treats each trade as a separate business, so a builder who also runs, say, a gardening round checks or adds both.

To sign in, GOV.UK says to use the same user ID and password you got when you registered for Self Assessment. GOV.UK lists 2 ways to sign in to HMRC online services: a Government Gateway user ID and password, or GOV.UK One Login with an email address and password. You may also be asked to prove your identity with a phone app and your passport or driving licence.

How CIS works once you are signed up

Records. Record what each job paid before the CIS deduction as income, with materials, tools and van costs as expenses. GOV.UK's CIS guidance says your income is your total pay before deductions, and the deductions are advance payments towards your tax and National Insurance, not an expense.

Quarterly updates. These are totals of your income and expense categories for the tax year so far, using the same categories as Self Assessment. HMRC's technical specification for the updates has no box for CIS deductions, and its box for other tax taken off trading income excludes them. In our reading, your turnover figure is the gross one. If you have a quiet spell between jobs, GOV.UK says you must still send the update.

Tax return. HMRC adds your CIS subcontractor deductions to your MTD tax return. You must check them against your monthly statements before you submit. GOV.UK says you cannot claim a refund in an MTD tax return, so any CIS refund is requested separately, through your HMRC online services account. The CIS refund guide shows how.

What an agent can do

An accountant, bookkeeper or managed service can sign you up through their HMRC agent services account, once you have authorised them. They need your full name, date of birth and National Insurance number, plus the business details above. Supporting agents can send quarterly updates, but only a main agent can submit your tax return. The agent authorisation guide walks through accepting their request.

What this means for you

If your pay before CIS deductions, 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. You can sign up now, for the current or next tax year. GOV.UK says 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.

If you were under £30,000, look at 2026-27. Over £20,000 means 6 April 2028.

Steps to sign up as a builder

1. Add up your 2025-26 gross pay from your monthly CIS statements, plus other self-employed work and any rent. The free MTD check shows your start date.
2. Check you are registered for Self Assessment and have filed a return in the last 2 years.
3. Choose MTD software that records gross pay and CIS deductions separately, 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 HMRC asks for, or authorise your agent and let them sign you up.
7. Keep every monthly CIS statement, ready to check the deductions HMRC adds to your tax return.

The trades section has more guides on CIS and MTD for the building trades.