IR35 Outside Determination Checklist UK | Status Review
Demonstrating genuine outside IR35 status is one of the most critical challenges facing UK contractors operating through a Personal Service Company. Without a clear, documented determination, HMRC can reclassify your engagement under Chapter 10 of the Income Tax (Earnings and Pensions) Act 2003, triggering significant back-tax liabilities for you or your end client. An IR35 Outside Determination Checklist provides a structured review of the key employment status indicators — substitution rights, control, and mutuality of obligation — creating an auditable paper trail that supports your position in any HMRC enquiry. This checklist helps contractors, recruiters, and hirers align contracts with real working practices before an engagement begins. Generate your IR35 Outside Determination Checklist now to protect your contracting status with confidence.
Generate your IR35 Agreement free →Key clauses in a IR35 Agreement
Right of Substitution
This clause confirms that the contractor retains the genuine right to send a suitably qualified substitute to perform the services, without requiring the client's personal approval of the individual. A credible, unrestricted substitution right is one of the strongest indicators of outside IR35 status under HMRC's employment status tests and has been repeatedly upheld in cases such as Autoclenz Ltd v Belcher.
Control and Direction Rights
This clause defines the extent to which the client can direct how, when, and where the contractor performs their services, ensuring the contractor retains meaningful autonomy over their working methods. Under Chapter 10 ITEPA 2003, excessive client control over day-to-day working practices is a primary indicator of deemed employment, making a clearly worded control clause essential to any outside IR35 determination.
Mutuality of Obligation Exclusion
This clause explicitly states that neither party is obliged to offer or accept further work beyond the current statement of work, eliminating the continuous obligation that characterises an employment relationship. Mutuality of obligation is a foundational test established in case law including Carmichael v National Power, and its absence is a key factor in demonstrating that no employment relationship exists under UK law.
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Generate free →Frequently asked questions
Who is responsible for completing an IR35 determination since the 2021 off-payroll reforms?
Since the off-payroll working rules were extended to the private sector in April 2021 under Chapter 10 ITEPA 2003, the responsibility for making an IR35 status determination shifted from the contractor to the end client, provided the client is a medium or large business. Small companies as defined by the Companies Act 2006 are exempt, meaning the contractor's PSC remains responsible for self-assessing its own status when engaging with them.
Can I use HMRC's CEST tool as my sole IR35 determination evidence?
HMRC's Check Employment Status for Tax (CEST) tool can form part of your evidence, and HMRC has stated it will stand by results produced when questions are answered accurately. However, CEST has been criticised by tribunal judges for failing to adequately assess mutuality of obligation, so relying on it alone without supporting contractual documentation and a record of actual working practices leaves your determination vulnerable to challenge.
What happens if my contract says outside IR35 but my working practices suggest otherwise?
HMRC applies a 'look behind the contract' approach, meaning the actual day-to-day working relationship takes precedence over what is written in the contract if the two are inconsistent. If an enquiry reveals that, in practice, you work fixed hours directed by the client, cannot substitute, and are treated as a permanent employee, HMRC can override the contractual wording and issue a determination of deemed employment under Chapter 10 ITEPA 2003, resulting in back tax and National Insurance liabilities.
The information on this page is for general informational purposes only and does not constitute legal advice. Contracto generates AI-assisted contract templates — they are not a substitute for advice from a qualified solicitor. For high-value or complex engagements, always seek independent legal review.