IR35 legislation states that an end hirer must take ‘reasonable care’ in assessing all contracts, to establish whether the individual would be seen an employee when carrying out the necessary work. If they fail to take reasonable care, the end hirer will be responsible for calculating the deemed direct payment, paying it over and reporting the tax and NICs that result.

CEST is an online tool HMRC have created to help companies establish whether or not a particular contract falls within IR35.