What is CEST?
CEST (Check Employment Status for Tax) is HMRC’s online tool for determining employment status for tax purposes, including whether the off-payroll working rules apply to a particular engagement.
For clients operating under the off-payroll rules, CEST is often used as part of the process of making an employment status determination and demonstrating reasonable care.
The tool asks a series of questions about the working arrangement and typically takes around 15 minutes to complete.
For engagements involving an intermediary such as a personal service company, the principal outcomes are:
- Off-payroll working (IR35) rules do not apply
- Off-payroll working (IR35) rules apply
- Unable to determine
CEST was first launched in March 2017, shortly before the implementation of the off-payroll rules in the public sector. It replaced an earlier Employment Status Indicator (ESI) tool.
The tool considers a range of employment status factors, including control, substitution and mutuality of obligation.
However, critics argue that it gives less weight than a tribunal might to the wider question of whether the worker is genuinely in business on their own account and to the overall commercial relationship between the parties.
What the possible outcomes mean
Off-payroll working rules do not apply
This result indicates that CEST considers the hypothetical relationship between the worker and the client not to be one of employment.
For an engagement through a personal service company, this broadly corresponds to what is commonly described as being outside IR35.
The result is only reliable if the information entered accurately reflects the contractual terms and actual working arrangement.
Off-payroll working rules apply
This result indicates that CEST considers the hypothetical relationship between the worker and the client to be one of employment for tax purposes.
This broadly corresponds to what is commonly described as being inside IR35.
Where the off-payroll working rules in Chapter 10 apply, the fee-payer is normally responsible for deducting PAYE income tax and employee National Insurance and accounting for employer National Insurance.
Where responsibility instead remains with the contractor’s intermediary under Chapter 8, the personal service company must consider the deemed employment payment rules.
An inside IR35 determination often makes contracting through a limited company less attractive for that particular engagement, although there may still be reasons to keep the company trading.
Many contractors instead work through umbrella companies, sometimes by choice and sometimes at the engager’s insistence.
Unable to determine
CEST can return an “unable to determine” result where the information supplied does not allow the tool to reach a definitive conclusion.
This is a problematic outcome because it provides no status determination that HMRC can stand behind.
The engager must therefore consider the case further rather than treating the CEST exercise as complete.
For this reason, we recommend professional IR35 status reviews for complex or high-value engagements, particularly where CEST cannot reach a conclusion.
What is HMRC’s stance on CEST?
The official position
HMRC states that it will stand behind CEST determinations where the information entered is accurate, remains accurate and the tool has been used in accordance with its guidance.
This assurance depends on the facts entered into the tool reflecting the true contractual and working arrangement.
If HMRC later concludes that the answers supplied did not accurately reflect the engagement, the CEST result may no longer provide protection.
What does “standing behind” mean in practice?
A valid CEST determination can provide significant protection, but it does not prevent HMRC from opening an enquiry.
In practice, a dispute may arise over whether the information supplied to CEST accurately reflected the engagement.
If HMRC concludes that the inputs were inaccurate, incomplete or no longer reflected the working arrangements, the parties may still face:
- Backdated tax assessments
- Interest on unpaid tax
- An IR35 investigation and the associated disruption
CEST does not provide immunity from enquiry. Its protection depends on the accuracy of the information supplied and on the engagement continuing to operate in the way described.
Why CEST is not a silver bullet
CEST is only as reliable as the information entered.
If the answers do not accurately reflect the contractual arrangement or the way the engagement actually operates, the result may provide little protection.
Care is also needed when comparing contractual wording with working practices.
In Autoclenz Ltd v Belcher [2011], the Supreme Court considered how tribunals should establish the true contractual agreement in an employment rights context.
However, the Court of Appeal in Atholl House Productions Ltd v HMRC confirmed that the special approach adopted in Autoclenz cannot simply be transplanted into an IR35 tax case.
In IR35 disputes, ordinary principles of contractual interpretation apply. Written contractual terms remain important, while the parties’ conduct and working practices may provide evidence when identifying the true agreement and assessing the hypothetical contract.
CEST also gives limited weight to some aspects of the wider employment status picture.
Business on own account (BOOA), for example, can form an important part of the overall assessment, particularly when considering the third stage of the employment status test illustrated by cases such as Atholl House and Kickabout Productions.
Likewise, whether a worker is part and parcel of the organisation can contribute to the overall employment status picture, as illustrated by cases including HMRC v PGMOL.
Employment status is ultimately determined by weighing multiple factors together.
Tribunals consider the relationship as a whole rather than relying on a single decisive test, and any rules-based questionnaire inevitably has limitations when dealing with complex factual situations.
Major criticisms of CEST
Accuracy concerns
Since its launch, CEST has faced sustained criticism from tax and legal professionals.
In 2019, the House of Lords Finance Bill Sub-Committee heard evidence that CEST produced outcomes inconsistent with known tribunal decisions in around 15% of cases examined by one witness.
Critics have also argued that the answers given to CEST can materially affect the outcome, making it particularly important that contractual rights and actual working arrangements are described accurately.
Oversimplification
Employment status law has developed through decades of case law.
In April 2025, HMRC updated CEST to include dedicated question sections covering areas such as Mutuality of Obligation (MOO) and Integration, alongside publishing its internal 72-route decision matrix.
The update provided greater visibility over how CEST reaches its conclusions, but it did not remove the underlying difficulty of reducing employment status law to a rules-based questionnaire.
Complex working arrangements, multiple-client businesses and broader commercial circumstances can be difficult to reflect fully through predetermined questions.
Factors which may require a wider qualitative assessment include:
- The commercial nature of the relationship
- Whether genuine financial risk exists
- Whether the worker is genuinely operating a business on their own account
- The wider economic and organisational reality of the engagement
The Hall v Lorimer judgment is frequently cited for the principle that employment status should be determined by considering the overall picture rather than mechanically counting individual factors.
The “unable to determine” problem
CEST can produce indeterminate results, leaving users without a definitive status conclusion.
Where this happens, the engager must consider the engagement further and reach its own determination using other evidence or professional advice.
HMRC’s published 72-route decision matrix showed that 34 of the 72 potential outcome paths led to an “unable to determine” result.
This helps explain why indeterminate outcomes remain a significant feature of the tool.
Try our free IR35 Status Checker. It examines the main employment status tests, including personal service, control and mutuality of obligation, alongside wider factors such as financial risk, integration and being in business on your own account.
The checker provides an independent indication of whether an engagement is more likely to fall inside or outside IR35. Like any automated status tool, it should not be treated as a substitute for professional advice in complex or high-risk cases.
Declining usage among businesses
Recent figures obtained by IR35 Shield under the Freedom of Information Act suggest that use of CEST has fallen sharply.
According to HMRC data, total CEST determinations fell from 458,894 in 2023/24 to 135,178 in 2025/26, a decline of 71% in two years.
The figures also showed that around one in five intermediary users continued to receive an indeterminate result.
While HMRC continues to support the tool, the decline suggests that some organisations may increasingly be using alternative status assessment processes, specialist IR35 advice or other internal procedures rather than relying on CEST alone.
For more detail, see our report on the sharp fall in CEST usage revealed by FOI data.
Limited scope
CEST is primarily an employment status assessment tool.
It does not replace the wider legal and compliance analysis required when applying the IR35 and off-payroll legislation.
For example, organisations may separately need to consider:
- Which part of the IR35 and off-payroll framework applies
- The impact of MSC legislation where relevant
- Whether the small company exemption means responsibility remains with the intermediary rather than the client
- Who is responsible for issuing a Status Determination Statement
- Who operates PAYE where the off-payroll rules apply
- Practical compliance and record-keeping obligations
These questions are separate from the underlying employment status test itself.
Ambiguous questioning
Some CEST questions have been criticised as ambiguous or difficult to apply to complex engagements.
Substitution is a particular example.
Case law such as Express & Echo Publications Ltd v Tanton demonstrates the importance that a genuine right of substitution can have when determining whether personal service is required.
However, the legal effect of substitution clauses depends on their precise wording and the wider contractual arrangement.
A genuine and sufficiently broad right of substitution may be inconsistent with an obligation to provide personal service, whereas a heavily restricted or merely nominal substitution provision may carry much less weight.
When should you use CEST?
CEST can be useful in straightforward cases and can form an important part of a client’s reasonable-care process.
HMRC states that it will stand behind a CEST determination where the information supplied is accurate and the tool has been used correctly.
CEST is not the only way to assess an engagement. You can also use our free IR35 Status Checker, which considers the main employment status tests alongside wider factors drawn from HMRC guidance and leading employment status case law.
For high-value, long-running or factually complex roles, clients and contractors may also wish to obtain a professional IR35 review rather than relying on any automated status tool alone.
This can involve expert status analysis, properly drafted contractual terms and clear evidence of how the engagement operates in practice.
A sound understanding of the relevant IR35 status tests remains important because the quality of any automated assessment ultimately depends on the accuracy of the information entered.
For clients making off-payroll determinations, using CEST can help demonstrate reasonable care. However, relying mechanically on the tool without checking that the answers accurately reflect the contractual terms and day-to-day working arrangement may undermine that position.