Is a Status Determination Statement legally required?

Yes. Under Chapter 10 ITEPA 2003, medium and large organisations in the private sector must issue a Status Determination Statement before making the first payment under a contract. Failure to provide one means the client (not the fee-payer or the PSC) becomes liable for any PAYE and NI that would otherwise be due.

Can I challenge a Status Determination Statement?

Yes. The off-payroll rules require medium and large clients to operate a disputes process. You must raise a disagreement in writing, and the client must respond with either a revised SDS or a written explanation of why they maintain their determination - within 45 days. If the client fails to respond within 45 days, the liability transfers to them regardless of the underlying status.

Does a Status Determination Statement expire?

An SDS reflects the working arrangements at a point in time. If the working arrangements change materially - new control arrangements, a substitution clause added or removed, a change in working location or hours - the original SDS may no longer be accurate. Clients should review and reissue SDSs if the underlying arrangements change.

What happens if no SDS is issued?

If no valid SDS has been issued, the liability for PAYE and NI defaults to the client - even if the work is genuinely outside IR35. The client cannot pass liability down the chain to an agency or fee-payer without first issuing a compliant SDS.

Does a small company need to issue an SDS?

No. The SDS requirement applies only to medium and large clients under Chapter 10. Where the end client is small (satisfying at least two of the three Companies Act 2006 size criteria), the off-payroll rules do not apply, and the contractor's PSC is responsible for self-assessing under Chapter 8.

What Is a Status Determination Statement?

A Status Determination Statement (SDS) is the formal document that a medium or large end client must issue when engaging a contractor through a personal service company. Introduced as part of the April 2021 private sector off-payroll reform, the SDS is the mechanism by which IR35 liability is passed down the supply chain - and the first thing any contractor should ask for when starting a new engagement.

The legal basis for an SDS

The SDS requirement is found in section 61NA of the Income Tax (Earnings and Pensions) Act 2003 (inserted by Finance Act 2020). The rules apply where all of the following are true:

The end client is a medium or large business (not a small company as defined by the Companies Act 2006)
The worker provides services through a personal service company or similar intermediary
The engagement is in the private sector (public sector has parallel rules under Chapter 10)

The SDS must be issued before or at the time the first payment under the contract is made. An SDS issued after payment has already been received is technically non-compliant, and liability remains with the client for any period before a valid SDS was in place.

What a valid SDS must contain

HMRC sets out that a valid SDS must include:

The determination itself: whether the engagement is inside or outside IR35 for the purposes of Chapter 10 ITEPA 2003
Reasons for the determination: a genuine explanation of the factors considered and why they led to that conclusion - not a generic template
The date the determination was made
Information about the disputes process: how the contractor can raise a disagreement and the timeframe for doing so

An SDS that simply states “inside IR35” or “outside IR35” without any reasoning is non-compliant. Courts and HMRC have been clear that the reasons requirement is substantive, not decorative. A compliant SDS needs to engage with the specific facts of the engagement - the degree of control, the substitution position, the MOO analysis, and any BOOA indicators.

What “reasons” actually means

A compliant SDS should explain which factors were considered - control over method and location, the substitution right and whether it was genuine, MOO indicators, integration factors - and how the balance of those factors led to the determination. One paragraph of boilerplate will not suffice. The more detailed and engagement-specific the reasons, the more defensible the SDS.

The liability chain

The SDS is the mechanism by which liability flows through the supply chain. Once a valid SDS has been issued:

The end client sends the SDS to the worker and to any agency immediately above them in the chain
The agency (or end client if directly engaged) becomes the “fee-payer” - responsible for deducting PAYE and NI from the payment to the PSC if the determination is inside IR35
If there is no valid SDS, the end client retains the liability - it cannot be passed down the chain without one

This means that for an inside-IR35 determination to be properly administered, the SDS must be issued and passed to the correct parties before any payment is made. A poorly administered supply chain - where SDSs are issued after engagement or not shared with the agency - creates tax risk for the end client.

Challenging an SDS: the disputes process

Contractors have a statutory right to challenge an SDS they disagree with. The process is:

The contractor (or any other party in the chain who believes the determination is wrong) raises a written representation to the end client
The end client must respond within 45 days - either with a revised SDS or a written explanation of why they maintain the original determination
If the client fails to respond within 45 days, liability reverts to them regardless of what the correct IR35 status would be
If the contractor remains dissatisfied after the disputes process, the matter can ultimately be referred to a tax tribunal

A well-prepared challenge will reference the specific facts of the engagement and explain how they apply to the relevant status tests - control, substitution, MOO, and BOOA. Simply expressing disagreement is not enough. The more evidence-based the challenge, the more likely the client will revise their determination.

SDS and small clients from April 2026

Following the April 2026 threshold changes, approximately 14,000 businesses that were previously medium are now classified as small. These clients no longer need to issue SDSs and are no longer subject to the Chapter 10 off-payroll rules. Contractors working with these clients now self-assess under Chapter 8.

If you previously had an SDS from a client that has now reclassified as small, that SDS no longer governs the position - you are back to self-assessing. This is an important change that many contractors affected by the April 2026 shift may initially miss.

Frequently asked questions

Is an SDS legally required?

Yes. Under Chapter 10 ITEPA 2003, medium and large clients must issue an SDS before making the first payment. Without one, the client bears the liability for any PAYE and NI due.

Can I challenge an SDS?

Yes. Raise a written disagreement with the end client. They must respond within 45 days with either a revised SDS or reasons for maintaining the determination. Failure to respond within 45 days transfers the liability to the client.

Does an SDS expire?

An SDS reflects the working arrangements at a point in time. If those arrangements change materially - new control terms, different substitution provisions, different location - the SDS should be reviewed and reissued if necessary.

What if no SDS is issued?

Without a valid SDS, liability defaults to the end client - even if the engagement is genuinely outside IR35. The client cannot pass liability down the chain without first issuing a compliant SDS.

Does a small company need an SDS?

No. The SDS requirement applies only to medium and large clients. Where the client is small under the Companies Act 2006, Chapter 10 does not apply and the contractor self-assesses under Chapter 8.