IR35 and the Status Determination Statement: What It Is, Why It Matters, and What HMRC Looks For

The contract says self-employed. The day-to-day reality says something else. The contractor sits in the client's office five days a week, works the hours the client sets, uses the client's equipment, attends the client's all-hands meetings, and has been doing this for the same organisation for three years.

HMRC looks at that arrangement and sees an employee. The contractor looks at it and sees a business relationship. The piece of paper that is supposed to resolve this disagreement — before it becomes a compliance investigation — is the Status Determination Statement.

An SDS is a written document issued by the client organisation that determines whether a contractor's engagement falls inside or outside IR35. For medium and large clients, it is a legal requirement. For the contractor operating through a PSC, it is the first line of defence. And when it is absent, wrong, or unsupported by the actual working arrangements, the tax liability that follows lands hard and lands upstream.

What IR35 Is and Why It Exists

IR35 — formally the off-payroll working rules — was introduced to address a specific problem: contractors who are, in substance, employees of the organisations they work for but who structure their arrangements through a limited company to avoid PAYE tax and NI.

The structure is familiar. A worker incorporates a personal service company. The PSC contracts with a client. The client pays the PSC. The PSC pays the worker a modest salary through PAYE, takes the rest as dividends, and the combined tax bill is lower than if the worker were employed directly.

Where the worker is genuinely in business — operating independently, taking real commercial risk, working for multiple clients, exercising real control over how and when they work — the structure is legitimate. Where the worker is, in all practical respects, an employee with a company number attached, HMRC's view is that the arrangement should be taxed as employment.

The SDS is the mechanism that forces the question to be answered formally, in writing, with reasons given.

What the SDS Must Contain

A valid SDS must:

State clearly whether the engagement is inside or outside IR35. Not "probably" or "likely." A determination.

Give the reasons for that conclusion. Not a boilerplate statement. Specific reasons based on the specific engagement — the actual working practices, the actual contractual terms, the actual day-to-day reality.

Be provided to the contractor before the engagement begins, or before any change in working arrangements that might affect the determination.

Be passed down the supply chain. If there is an agency between the client and the contractor's PSC, the SDS must be given to both the contractor and the agency.

An SDS that simply states "outside IR35" with no reasoning is not a compliant SDS. HMRC can challenge a determination and request the evidence that supports it. If no reasoning exists and the working practices suggest an employment relationship, the determination will not withstand scrutiny.

The Three Tests HMRC Applies

Substitution. Can the contractor send someone else to perform the services? A genuine business can substitute — if Mark is ill, the PSC can send another qualified person. An employee cannot substitute — the employer hired Mark specifically, and Mark must turn up.

The substitution right must be real. A contract clause permitting substitution that has never been exercised and would never be permitted in practice is not genuine substitution. HMRC looks at whether substitution has actually happened or could realistically happen, not just whether the contract mentions it.

Control. Who decides how, when, and where the work is done? An independent contractor operates with a brief — deliver this outcome by this date, using your own methods. An employee is told when to start, where to sit, which processes to follow, and how to do the work.

The more control the client exercises over the method of work — as opposed to just the output — the more the engagement looks like employment. Direction over daily tasks, mandatory attendance at internal meetings, requirement to follow the client's processes rather than the contractor's own — all of these are control indicators.

Mutuality of obligation. Is the client obliged to keep offering work? Is the contractor obliged to accept it? In an employment relationship, the answer to both questions is typically yes — the employee turns up and the employer pays them. In a genuine contracting relationship, each project is negotiated independently, the client has no obligation to offer more work, and the contractor has no obligation to accept.

Long-running engagements with the same client, automatically renewed, where it would feel strange for either party to not continue — these score against the contractor on mutuality of obligation.

What HMRC Does With a Challenged SDS

HMRC's IR35 compliance activity focuses on engagements that look like employment on the surface — same client for two years, daily attendance, integrated into the client's team — while being structured as outside IR35 on paper.

When HMRC opens an IR35 enquiry, they request: the SDS and the reasoning behind it, the actual contract between the PSC and the client, evidence of substitution rights being exercised or available, evidence of financial risk taken by the PSC, and witness evidence about how the engagement operated day to day.

The contract is starting point, not endpoint. HMRC will interview both the contractor and the client if the written arrangements don't match the reality. A contract drafted to look independent, sitting on top of a working relationship that looks like employment, does not survive scrutiny.

Why Director-Only PSCs Need Clean Payroll Records

The payroll record of the PSC is part of the evidence base. A director operating outside IR35 who takes a regular director's salary, files monthly RTI, issues payslips, and maintains clean payroll records demonstrates that the PSC is operating as a genuine business with proper employment of the director.

A director who has been informally drawing money from the company, with gaps in RTI, no payslips, and no P60, has a payroll record that looks like someone who is treating the limited company as a personal bank account rather than a genuine business vehicle. In an IR35 investigation, that record is additional ammunition for HMRC.

Clean payroll is not just about payroll compliance. For a PSC operating outside IR35, it is part of the evidence that the business is real.

bookd. manages director payroll for PSC contractors — monthly RTI, correct salary level, P60 at year end, clean HMRC record. If you're operating outside IR35 and your payroll record has gaps, the documentation that supports your status determination is incomplete. That's a fixable problem. It is easier to fix now than during an enquiry.