CEST (Check Employment Status for Tax)
UK tax glossary · Last reviewed: April 2026
CEST is used by businesses and workers to establish IR35 status (inside or outside IR35) for contractor arrangements. HMRC states it will stand by the result of a CEST determination if the information entered is accurate and the tool is used correctly.
The tool asks about control, substitution, and mutuality of obligation — the three classic employment status tests. If CEST is unable to determine status, you may need professional advice or legal analysis.
For public sector and medium-to-large private sector engagements, the end client (not the contractor) is responsible for determining IR35 status and running CEST. Small private-sector businesses are exempt from the off-payroll rules.
Common questions
Is a CEST result legally binding?
Not in law — tribunals can reach different conclusions. However, HMRC commits not to investigate status on its own initiative where CEST has been used correctly and the facts have not changed.
What happens if my engagement is 'inside IR35'?
The fee-payer deducts Income Tax and NI as if you were an employee, even though you invoice through a limited company. You lose the tax flexibility of contracting through a personal service company.
Related resources
TaxHelper provides general information based on published HMRC rates and guidance. It is not regulated financial or tax advice. For decisions involving significant sums, complex circumstances, or if you are unsure, speak to a qualified accountant or HMRC directly.