How Do Contractor Interviews and IR35 Status Checks Work in the UK?

Contractor interviews in the UK are shorter and more skills-focused than permanent hiring, often a single 45-minute call, but they come with an IR35 status determination that decides whether you are taxed like an employee (inside) or as a business (outside). Since April 2021 medium and large clients make that determination, not you, and they must issue a Status Determination Statement before the engagement starts. Inside-IR35 roles are typically paid via an umbrella company; outside roles can be invoiced through your limited company.

Key facts

The specifics, before the explanation.

Medium and large private-sector clients and all public bodies have decided IR35 status since 6 April 2021; small companies leave the decision with the contractor
A Status Determination Statement (SDS) must be given to you with reasons, and you can dispute it with the client within a formal process
From 6 April 2026, umbrella company PAYE compliance becomes the responsibility of the recruitment agency or end client in the labour supply chain, changing how inside-IR35 pay is handled
Outside-IR35 contracts usually pay a higher day rate but carry substitution, control and mutuality-of-obligation tests
HMRC's CEST tool is the standard employment status check and its result is accepted if the inputs are accurate

What this actually means

Expect the client to have decided IR35 status before the advert goes out; agencies now list "inside" or "outside" on the role. Read that first, because it changes your take-home pay by a large margin and your working arrangements. If a role is advertised as outside IR35, the interview will probe whether you operate like a business: can you send a substitute, do you control how the work is done, is there a defined deliverable rather than open-ended attendance.

The interview itself is usually one round with the hiring manager and sometimes a technical peer. They want to know whether you can start on Monday and be useful by Wednesday, so lead with the most recent, closest-matched engagement, the tools you used, and what you shipped. Culture-fit questions are rare; availability, notice, rate and day one readiness are not.

On rate, know your inside and outside numbers before the call. The same role paid inside IR35 through an umbrella can leave you 20 to 30 per cent worse off after employer National Insurance and umbrella margin, so a single rate for both does not work. Ask which it is and quote accordingly.

Be ready to describe past engagements in a way that supports the determination the client wants to make. That is not coaching the facts, it is telling them plainly. Rehearse a two-minute summary of your last three contracts out loud until you can give it without reading, because the call will be short and the agency may be comparing you with four other people the same afternoon.

What to actually do

Rules and figures move. Confirm anything time-sensitive with the official regulator before you rely on it.

Confirm the advertised IR35 status and whether a Status Determination Statement already exists before quoting a rate
Prepare separate inside and outside day rates and be able to explain the gap in one sentence
Have a one-page summary of your last three engagements with tools, outcomes and dates ready to talk through
Rehearse a two-minute spoken summary of your contracting history out loud; contractor calls are short and time-boxed
Check the umbrella company against the FCSA or Professional Passport accredited lists before accepting an inside role

Frequently asked questions

Can I challenge an inside-IR35 determination?

Yes. The client must have a client-led disagreement process and respond within 45 days with reasons. In practice many contractors simply decline the role instead.

Do I need a limited company to contract?

Only for outside-IR35 work. Inside-IR35 roles are usually paid through an umbrella company on PAYE, and many contractors keep a dormant company for outside opportunities.

Are contractor interviews easier than permanent ones?

Shorter, not easier. The bar is immediate competence on the stack and availability, and there is less tolerance for vague answers because there is no onboarding period.

Sources

Referenced for this guide:

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