The Construction Industry Scheme (CIS) sets out the rules for how payments to subcontractors for construction work must be handled by contractors in the construction industry.
The scheme applies mainly to contractors and subcontractors in mainstream construction work, however businesses or organisations whose core activity isn't construction but have a high annual spend on construction may also count as contractors and fall under the scheme.
As a contractor you have certain obligations under the scheme, including registering 
with the scheme, checking whether your subcontractors are registered with HM Revenue & Customs (HMRC), paying subcontractors and submitting monthly returns.
If you are a subcontractor, you need to register with HMRC - as well as your main business name you can register up to one trading name. You must also keep HMRC informed of any changes to your business (including changes to the structure, address, business name, partners etc).
Intro to CIS 
What you must do CIS HMRC Guide340 to CIS
CIS Reform Manual
If you require any assistance with CIS please contact me. Dermot Murphy Tax Partner.