About IR35 Checker

IR35 Checker gives UK contractors a fast, affordable first look at their IR35 risk — based on the contract they've actually been sent and how they'll actually work — so they can negotiate better terms, check a Status Determination Statement, or decide whether they need a specialist.

Why we built it

A specialist IR35 contract review typically costs £49–£125 or more and takes days. HMRC's free CEST tool is quick but never reads your contract. Most contractors sign somewhere in between — without knowing which of their clauses help them and which hurt. We built IR35 Checker to close that gap.

How the analysis works

1. We read the whole document. Your contract (and optional SDS or upstream terms) is passed in full to a large language model from Anthropic — not just the first few pages, and including scanned PDFs.
2. We combine it with your working practices. Your answers to 12 questions describe the reality of the engagement, which tribunals weigh heavily.
3. We apply a fixed legal framework. The model is instructed to use the three-stage test from Ready Mixed Concrete (1968), the Supreme Court's guidance on mutuality and control in HMRC v Professional Game Match Officials [2024] UKSC 29, the Court of Appeal's approach to the hypothetical contract in HMRC v Atholl House Productions [2022] EWCA Civ 501, and the principle in Autoclenz v Belcher [2011] UKSC 41 that terms which don't reflect reality can be disregarded.
4. Everything is evidenced. Each factor cites the clause it relies on, and says so when the contract is silent. Where your answers contradict the contract, we flag it.
5. We never give a verdict. Reports describe risk and indicators. They never say "inside" or "outside" IR35, because only HMRC or a tribunal can decide that.

What it can't do

It is not a lawyer, a tax adviser or insurance. It relies on the documents and answers you give it, and AI can make mistakes. For high-value engagements, an HMRC enquiry or anything you're unsure about, take your report to a qualified IR35 specialist or accountant — it will make that review quicker.

Your data

Your contract is deleted as soon as your report is ready, and the report is deleted after 30 days. Our AI provider does not use your documents to train its models. Read the full privacy notice.

Get in touch

Questions, feedback or a problem with a report? Contact us.