You must register as a contractor with the Construction Industry Scheme (CIS) if:
• you pay subcontractors to do construction work
• your business doesn’t do construction work but you usually spend more than £1 million a year on construction
You may be a sole trader, in a partnership or own a limited company.

You should register for the Construction Industry Scheme (CIS) if you work for a contractor and you’re either:
• self-employed
• the owner of a limited company

Under CIS, a contractor must deduct 20% from your payments and pass it to HM Revenue and Customs (HMRC).
These deductions count as advance payments towards your tax and National Insurance bill.
If you don’t register with the scheme, contractors must deduct 30% from your payments instead.
If you don’t want deductions to be made in advance by contractors, you can apply for ‘gross payment status’ after you’ve registered with CIS. This means you’ll pay all your tax and National Insurance at the end of the tax year.

You don’t need to register with CIS if you’re an employee. Check your employment status if you’re not sure.