IR35 in practice

Three tests, and none of them is the contract

The written agreement is evidence, not the answer. What decides status is the working arrangement it describes, and whether that arrangement is what actually happens on a Tuesday.

Test one

Control

Who decides what gets done, how it gets done, when, and where. A client is entitled to say what the outcome must be; the further they go into how, the worse it looks.

Points your way

you choose the method and the order of work
no line manager, no appraisal, no team meeting you must attend
you work where the job needs doing, not where a desk was allocated

Points the other way

a rota, a shift pattern or core hours imposed on you
tasks reassigned to you mid-contract that were never in the schedule
an induction, a lanyard and a place on the internal org chart

Test two

Substitution

Could you send somebody competent in your place and pay them yourself? Not whether you would — whether the client would have to accept it.

A clause that lets the client refuse a substitute "at its sole discretion" is worth almost nothing. One that has actually been used, once, with an invoice to prove it, is worth more than any amount of drafting.

Test three

Mutuality of obligation

Is the client obliged to keep finding you work, and are you obliged to take it? A contract that runs on regardless of whether there is anything to do starts to look like employment.

This is the test people quote most and evidence least. If your contract ends when the project ends, say so plainly — and check the notice clause does not quietly turn it into a rolling arrangement.

What a status determination has to contain

If the end client is a medium or large business, they must produce one, pass it to you and to the agency, and give reasons. "Inside, per group policy" is not a reason.

The conclusioninside or outside, for this engagement, not for the department
The reasoningwhich facts led there, in enough detail that you can argue with them
Reasonable caretaken by the client. A blanket decision across every contractor is the textbook failure of it
A route to disagreeyou write, they have 45 days to respond with a reason, and the determination stands until they do

Small companies are outside the off-payroll rules entirely, and then the old position applies: the responsibility for getting status right stays with your own company. People often discover this after a year of assuming somebody else was deciding.