Status Determination Statements (SDS) Explained

What is a Status Determination Statement?

A Status Determination Statement (SDS) is the formal written assessment a medium or large client must produce for each contractor engagement, determining whether the role falls inside or outside IR35. The requirement was introduced for public sector bodies in 2017 and extended to the private sector in April 2021.

Before the 2021 reform, it was the contractor's own company that assessed IR35 status. The reform transferred this responsibility to the end client for most engagements — with significant consequences for who bears the tax risk of getting the determination wrong.

Who must issue an SDS?

What must an SDS contain?

HMRC's legislation (ITEPA 2003, s61NA) requires the SDS to include:

1. The determination — inside or outside IR35
2. The reasons for that determination

The reasons must be specific to the individual engagement. A blanket statement that "all contractors are considered inside IR35" does not comply with the legislation — it does not provide engagement-specific reasons. However, many large organisations issue these anyway, and challenging them formally is difficult in practice.

The supply chain and who is responsible

In a typical agency supply chain:

1. End client — determines status and issues SDS to the agency and contractor
2. Agency (fee-payer) — receives the SDS, operates PAYE if inside IR35
3. Contractor's company — receives the SDS, invoices the agency

If the end client fails to issue an SDS, PAYE responsibility defaults to the client — not the agency or contractor. This is a significant legal protection for contractors, though enforcing it in practice requires the dispute process.

The disagreement process: step by step

If you receive an inside IR35 SDS and believe it is wrong, you have the right to challenge it:

1. Write to the client with your specific grounds for disagreement. Provide evidence: contract analysis, working practice summary, CEST result, professional review if available.
2. The client must respond within 45 days with either: a revised SDS, or confirmation of the original determination with reasons.
3. If the client confirms inside IR35 and you remain unsatisfied, raise the dispute with HMRC through their Employment Status and Intermediaries team.
4. Ultimately, only an employment tribunal or the Upper Tribunal can definitively determine IR35 status.

Does an SDS protect you from HMRC investigation?

An SDS is the client's determination, not HMRC's. HMRC can still investigate and reach a different conclusion. However, HMRC has confirmed it will not pursue contractors where the client made an incorrect determination in good faith, using reasonable care — the tax risk transfers to the fee-payer in that scenario.

This is an important protection: if the client incorrectly determines you are outside IR35, and HMRC later disagrees, the tax and NI liability falls on the fee-payer (client or agency), not on your company — as long as you did not act fraudulently or provide misleading information.

Blanket inside-IR35 SDSs: what to do

Large organisations sometimes issue blanket SDSs covering all contractors, often driven by risk aversion rather than genuine individual assessment. If you receive one:

• Request the specific reasons for your engagement's determination (you are entitled to these)
• Consider using the disagreement process if you have strong grounds
• Negotiate a rate uplift to compensate for the tax difference
• Assess whether the engagement is still commercially viable at the inside-IR35 tax cost

Common mistakes

• Accepting an SDS without reading the reasons — if the SDS lacks engagement-specific reasons, it may not be legally compliant. Request the full rationale.
• Missing the 45-day response window — if you want to challenge, initiate the disagreement process promptly. Clients are not obliged to extend the window.
• Assuming the SDS is permanent — an SDS applies to a specific engagement. If the engagement renews or materially changes, a new SDS should be issued. A change in working practices can change the status determination.