Registering as Self-Employed for Construction: Step by Step

‍‌​​​​​​​‌​​‌​​‌‌​​​​​​‌‌​‌​​‌‌​‌‍SiteKiln gives you plain-English information, not legal advice. If you need advice specific to your situation, talk to a qualified accountant or tax adviser.

The short version

If you're working for yourself in construction, you need to tell HMRC you're self-employed and (because it's building work) you'll normally also register for CIS as a subcontractor. You do this once, online, and HMRC give you a UTR number, then contractors can verify you and take CIS at the right rate.

Why it matters

If you don't register, HMRC can fine you for late registration and late tax returns, and you'll find it harder to sort things out later. Contractors may have to take 30% CIS off your pay instead of 20%, which hits your cashflow straight away. Getting on the system early means normal CIS deductions and clear paperwork for refunds or tax bills.

If you're working for yourself in construction (labour only or supplying materials), HMRC see you as self-employed, and you need to be registered for Self Assessment -- and usually CIS as a subcontractor. You can sort both online in under an hour if you've got your details ready.

Step 1 -- Decide: are you actually self-employed?

You're usually self-employed if:

• You work for several firms, not just one, over a year.
• You can send someone else in your place or bring a mate to help.
• You use your own tools, van and insurance, and you quote per job, day rate or price work -- not salary.
• You don't get holiday pay, sick pay or a company pension.

If in doubt, it's safer to register and then adjust later than to ignore it and hope HMRC don't notice.

Step 2 -- Register for Self Assessment (SA)

You must register for Self Assessment if:

• You earn more than £1,000 a year from self-employment (turnover, not profit).
• You're getting CIS statements from contractors (they're already telling HMRC you exist).

To register:

• Go to GOV.UK and register as a new self-employed sole trader for Self Assessment.
• You'll need: full name, address, date of birth, National Insurance number, what you do (for example "self-employed carpenter"), and the date you started trading.
• HMRC will set up a Self Assessment record and send you a Unique Taxpayer Reference (UTR) by post.

That UTR is your tax ID number for life.

Step 3 -- Register for CIS at the same time

Because you're in construction, you also need to register under the Construction Industry Scheme (CIS) as a subcontractor.

The clean way if you're new:

• When you register for Self Assessment online, choose that you're working as a subcontractor.
• This registers you for Self Assessment and CIS in one go.
• You'll end up with a UTR and CIS status so contractors can verify you and deduct the correct rate.

If you're already registered as self-employed:

• Log into your HMRC online account and add CIS as a subcontractor, or
• Call the CIS helpline and register over the phone using your UTR and NI number.

Step 4 -- What contractors will ask you for

Once you're registered, every contractor will want:

• Your full name and any trading name.
• Your UTR.
• Your National Insurance number.
• Company details if you trade through a limited company.

They use this to verify you with HMRC, which tells them whether to deduct CIS at 20% (standard), 30% (if you're not matched/registered), or 0% if you have gross payment status.

Step 5 -- Deadlines and what happens next

Once you're registered:

• You must file a Self Assessment tax return every year, showing all your construction income and costs, plus CIS tax already deducted.
• HMRC use this to work out whether you still owe tax and National Insurance, or if you're due a refund.
• You must register for Self Assessment by 5 October after the end of the tax year when you started, and file your return by 31 January after the tax year if filing online.

If you're already late, registering now usually makes things easier to sort than waiting.

Checklist -- getting set up

Use this as your "first week" list:

• Decide if you are genuinely self-employed (more than one client, no holiday pay, your own kit).
• Register as a self-employed sole trader for Self Assessment on GOV.UK.
• When asked, tick/choose that you're working as a subcontractor so CIS is added.
• Wait for your UTR letter and keep the number somewhere safe.
• Give your UTR and NI number to contractors so they can verify you for CIS.
• Start keeping basic records: invoices, CIS statements, receipts, bank statements.

What to do next

• Register for Self Assessment as a sole trader on GOV.UK if you have not already.
• Add CIS subcontractor status at the same time so contractors can verify you at 20% instead of 30%.
• Keep your UTR somewhere safe -- you will need it for every contractor and every tax return.
• Set up a simple record-keeping system from day one: invoices, CIS statements, receipts, bank statements.
• Talk to an accountant before your first January deadline so you are not scrambling.

Sources and legislation

• Income Tax (Earnings and Pensions) Act 2003 -- framework for employment vs self-employment status. legislation.gov.uk/ukpga/2003/1
• Finance Act 2004 -- Construction Industry Scheme rules for contractors and subcontractors. legislation.gov.uk/ukpga/2004/12
• Social Security Contributions and Benefits Act 1992 -- National Insurance obligations for the self-employed. legislation.gov.uk/ukpga/1992/4
• HMRC CIS340 -- HMRC's public guide for contractors and subcontractors. gov.uk/government/publications/construction-industry-scheme-cis-340

Related guides on this site

• 5.2 CIS registration and verification
• 5.3 Filing Self Assessment -- construction-specific deductions
• 5.6 Expenses you can claim
• 5.15 Record keeping
• S9 Setting up as a sole trader -- step by step
• 8.1 Sole trader vs limited company -- honest comparison

This topic is sponsored by The Online Accountant.

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