CEST tool: how to check IR35 status
HMRC's Check Employment Status for Tax tool, known as CEST, was last enhanced on 30 April 2025 to simplify its language and fold in cases that previously needed separate guidance [1]. It matters because HMRC commits to standing by the result the tool produces, provided the information entered is accurate and matches its guidance [1]. For a set of rules that generated an estimated £4.2 billion in additional tax between October 2019 and March 2023, a free, authoritative status check is a valuable starting point [7].
This guide sets out what CEST does, what information to gather before starting, how to run it, how to read the result, and what an engager must do once a determination is made.
Key takeaways
- CEST gives HMRC's view of a worker's employment status for tax, based on the answers provided [1].
- HMRC stands by the result where the information is accurate and consistent with its guidance [1].
- Anyone can use the tool, and it is anonymous, but progress cannot be saved, so all information must be ready first [1].
- The saved result can be used as a valid status determination statement [1].
- In finely balanced cases the tool can return an "unable to determine" outcome, which is a valid result [5].
What the CEST tool is
CEST checks whether a worker on a specific engagement should be classed as employed or self-employed for tax, and whether the off-payroll working rules apply [1]. A worker's status for tax decides who is responsible for working out the Income Tax and National Insurance due and paying it to HMRC [1].
Anyone can use it: hirers, workers, agencies or third parties [1]. The tool is anonymous and HMRC does not collect identifying details of those using it, so a hirer can run it even before a worker is named [1]. It is the tool HMRC points to for administering the off-payroll working rules, and businesses running their own HMRC-recognised payroll software still use CEST for the status decision that sits upstream of any payroll run.
What to gather before starting
CEST cannot save progress, so every input needs to be to hand before opening it [1]. There must also be a contract in place or expected, whether written, verbal or implied [1]. The table below lists what the tool asks about.
| Area | What CEST needs to know |
|---|---|
| The contract | Its terms and duration [[1]](https://www.gov.uk/guidance/check-employment-status-for-tax) |
| Responsibilities | The worker's duties on the engagement [[1]](https://www.gov.uk/guidance/check-employment-status-for-tax) |
| Control | Who decides what work is done, and when, where and how [[1]](https://www.gov.uk/guidance/check-employment-status-for-tax) |
| Payment | How the worker will be paid [[1]](https://www.gov.uk/guidance/check-employment-status-for-tax) |
| Benefits | Any corporate benefits or reimbursed expenses [[1]](https://www.gov.uk/guidance/check-employment-status-for-tax) |
Accountants running determinations across many client engagements usually keep these inputs in one place, often a multi-client payroll dashboard, so each answer can be evidenced if HMRC later asks how a determination was reached [5].
How to run CEST and read the result
The tool is completed online in a single sitting, and afterwards the user can save and print both the answers and the result [1]. It works through the employment status tests, weighing factors such as control, personal service and financial risk, and HMRC publishes the breakdown of results and the logic the tool uses [4]. Where a contract or working arrangement changes, the tool can be run again to check whether the result still holds [1].
The 'unable to determine' outcome
CEST is not designed to produce a definitive answer in every single case. In finely balanced engagements it can return an "unable to determine" result, which HMRC treats as a valid outcome rather than an error [5]. When that happens, the engager must reach a decision another way, using HMRC's wider guidance on making status determinations and taking reasonable care over the judgement [5].
What to do after a determination
A CEST result can serve as a status determination statement, the document a medium or large client must produce and pass down the labour supply chain [6]. The client passes it to the party it contracts with and to the worker, and keeps passing it down until it reaches the fee-payer immediately above the worker's intermediary [3].
If the result is that the worker is employed for tax, the deemed employer then deducts PAYE and employee National Insurance and pays employer National Insurance, reporting it through Real Time Information with the off-payroll worker indicator set [3]. Payroll that holds the HMRC Recognised badge applies that indicator automatically, and platforms embedding UK payroll can trigger the deduction through an HMRC-recognised payroll API. The financial size of that deduction is covered in the guide to how an IR35 calculator works, and the wider rules sit in the overview of IR35 meaning.
Conclusion
CEST is the free, HMRC-backed first step in an IR35 decision, and its value depends entirely on the accuracy of the answers fed into it. A determination reached with careful, evidenced inputs carries HMRC's standing behind it; a rushed one does not. The engager who prepares the contract detail, control facts and payment terms before opening the tool gets a defensible result in a single session.
The determination is only the start. Once a worker is inside the rules, the obligation moves to running and reporting the deduction correctly, on time and with the right indicator. Treating CEST and payroll as two halves of one process, rather than separate tasks, is what turns a status check into genuine compliance.
Frequently asked questions
Is the CEST result legally binding on HMRC?
HMRC commits to standing by a CEST result as long as the information entered remains accurate and is used in accordance with its guidance [1]. That protection falls away if the answers do not reflect the real working arrangement. Keeping the saved answers and result on file is what evidences that the determination was made with reasonable care [5].
Can CEST be used as a status determination statement?
Yes. After completing the tool, the user can save the answers and result and use that result as a valid status determination statement [1]. A medium or large client must then pass the statement to the worker and down the labour supply chain to the fee-payer [3].
What if CEST cannot determine the status?
An "unable to determine" result appears in finely balanced cases and is a valid outcome, not a fault [5]. The engager must then make the decision using HMRC's wider guidance on employment status, documenting the reasoning. Taking reasonable care over that judgement is what protects the engager if the determination is later questioned [5].
Who should run the CEST check?
Anyone can, but responsibility for the determination depends on the client [1]. For public-sector and medium or large private-sector clients, the client makes and issues the determination; for a small private-sector client, the worker's own intermediary does [2]. Whoever carries that responsibility should be the one running CEST and keeping the record.
