You can sign up on the HMRC CIS website or by calling the service. You will need your UTR number or, if you are dealing as a business, the UTR number of your business. You’ll also need information about yourself, like your National Insurance number. Then, if a worker wants to hire you, he or she will be able to check your CIS status online. The contractor can then take 20% tax off your bill. If you’re not listed with CIS, the contractor should take 30% off your bill.