What is the CEST tool?

CEST, Check Employment Status for Tax, is HMRC's free online tool that asks a series of questions about a working arrangement and gives a determination of employed or self-employed for tax purposes. HMRC will generally stand by a CEST result if it's used correctly and the answers accurately reflect the actual working practices, but the tool has been criticised for not fully capturing every factor that matters in case law, particularly mutuality of obligation. It's a useful starting point, but many contractors get an independent contract review alongside it, especially for borderline cases.