Self Assessments for Self-Employed Contractors

Guidance on self assessment requirements for those working under the Construction Industry Scheme


All self employed individuals must submit a self assessment to HMRC each fiscal year (running from 6th April to the 5th April) and the Construction Industry Scheme is no different. The self assessment is due no later than the 31st January following the end of the fiscal year.

This self assessment details all income you have received through your business as well as any expenditure for example costs such as materials, travel for work and so on. So although NASA CIS will process the applicable CIS deductions (usually 20%), you may well have other income from other umbrella providers or other work that you will need to consolidate and declare.

The self assessment will calculate your annual earnings and expenditure and determine the level of tax that is due on that income. Where there is a balance to pay, you will be required to make payment direct to HMRC. This may be the case even if NASA CIS or another provider has retained the correct CIS % on your payments.  


NASA Consulting offer a stand alone self assessment service - One of our highly experienced accountants would chat through your individual requirements and provide you with clear an transparent pricing before you go ahead. 

For more information please contact our sales team on or complete our enquiry form: Nasa CIS - Self Assessment 



NASAs CIS does not support the claiming of expenses or materials costs directly through your weekly payroll process. We recommend that you claim any such expenditure that you incur directly on your self assessment each year.

Remember to:

  • Keep records of your expenditure including the date, item description, total costs, the end client or assignment that the cost relates to (a spreadsheet is a great way to log this information)
  • Keep all receipts for any costs that you wish to claim (HMRC require these to be kept) as either originals or copies (scanned etc)
Should you have an existing relationship with an accountant who completes your self assessment already, then provide this information to them in good time to be able to complete your self assessment before the deadline. Any tax relief will be provided to you though your return.