https://www.gov.uk/register-for-self-assessment
Use this link to register for self-employed, once you have completed this you will be given a UTR number usually via post. As soon as you have this, you will need to call the CIS helpline or registering at 20% tax via the government gateway. If this is not done by the time of you being paid, it will automatically tax you at 30%. If you need any help do not hesitate to get in touch.
CIS Registration Note:
If you are not currently registered for CIS (Construction Industry Scheme) with HMRC, you must register before we can make standard payments.
Unregistered subcontractors are subject to the default 30% tax deduction, as required by HMRC.
To register as a subcontractor:
Visit the HMRC site: Register for CIS as a subcontractor
Alternatively, call the HMRC CIS helpline: 0300 200 3210
Once registered, please provide your UTR (Unique Taxpayer Reference) and CIS status so we can verify with HMRC and apply the correct deduction rate (20% or 0%).