Every IR35 questionnaire, including HMRC's own CEST tool, is asking three things in many different ways: who controls the work, whether you personally must do it, and whether either side is obliged to carry on. Everything else is context that tips a borderline case. Knowing which of the three a question belongs to is what stops you answering honestly and still producing a determination that does not match your engagement, which is the commonest way a good arrangement gets called inside.
Control: the questions, and what they are getting at
Does the client decide what you work on next, or does the contract? Can the client move you to different work without a new agreement? Who sets your hours, and are they yours or the client's? Where is the work done, and is that a requirement or a convenience? Who decides HOW the work is done, which is the one that matters most: a client that specifies the outcome is a client, and a client that specifies the method is an employer. Answer these about the engagement as a whole rather than about a good week.
Personal service and substitution
Must you do the work yourself? Could you send a suitably qualified substitute, and would you pay them? Has anyone ever done so, on this engagement or another? Would the client have to agree, and on what grounds could it refuse? A right to substitute that exists but is subject to client approval of the individual is normal and still helps; a right that the client may refuse for any reason at all is worth very little. The strongest answer is one that has actually happened.
Mutuality of obligation, and why it is argued about
Must the client offer you work, and must you accept it? Is there an obligation to be available between pieces of work? What happens if the work runs out before the end date: are you paid, or released? Mutuality is the most disputed of the three, because CEST is widely criticised for not weighing it the way the case law does, and because almost every engagement has some mutuality inside its own term. The distinction that matters is between an obligation to complete THIS piece of work and an obligation to keep providing work and accepting it.
The questions that tip a borderline case
Do you take financial risk: fixing defects at your own cost, carrying professional indemnity insurance, being paid for a deliverable rather than for time? Do you provide your own significant equipment? Do you work for other clients, or could you? Are you integrated: a job title, line management, a place in the org chart, an entry in the internal directory, an invitation to the staff Christmas party? None of these decides an engagement alone and several together decide most of them.
Why the same answers produce two determinations
Because the questions are about judgement and the weighting is not fixed. CEST returns a determination HMRC says it will stand behind if the answers are accurate and the working practices match, and it returns "unable to determine" on genuinely balanced cases. A client's own questionnaire may weight integration more heavily, or may have been designed to produce inside answers so the client carries no risk. If you disagree with the result, the route is representations to the client, which must respond within 45 days with a new determination or its reasons.
Questions people ask about ir35 questionnaire
What are the IR35 assessment questions and answers that matter?
Control over the work, whether you must do it personally, and whether either side is obliged to offer and accept more. Everything else, financial risk, equipment, other clients and integration, tips a borderline case.
Is mutuality of obligation part of CEST?
CEST handles it lightly, which is the main criticism made of the tool: it treats the existence of a contract as implying enough mutuality, where the case law asks whether there is an obligation to offer and accept work beyond the current piece.
Will HMRC stand behind a CEST result?
HMRC says it will stand behind a CEST determination provided the answers given are accurate and the working practices match them. Keep the printout and the date, because both conditions are about facts rather than about the tool.
What if my client's questionnaire gives a different answer?
Make representations to the client. It must respond within 45 days with either a new Status Determination Statement or the reasons for keeping the old one, and a documented review of the working practices is what makes that argument land.