Home / IR35 Tools Compared
IR35 tools compared, 2026
Ten tools, four categories, and one table. What each one actually answers, what it costs, and how you get to it, including the cases where we are not the right choice.
Status and contract review tools
These answer the question "is this engagement inside or outside IR35". They do not tell you what the answer costs you. Ordered free self-serve tools first, then the insurance-backed providers who pair a human review with cover, and within that group by breadth of cover rather than by price.
| Tool | What it answers | Price | Access | Shows reasoning |
|---|---|---|---|---|
| HMRC CEST | Employment status | Free | Direct, gov.uk | None. Returns a label only |
| IR35 Verdict | Status probability and take-home | Free scan, £9.99 report | Direct, no account | Six dimensions, case law cited |
| IR35 Shield | Employment status | Free assessment | Direct, account required | Case law led, definitive result |
| Kingsbridge | Status, human review, cover | Bundled with IR35 Protect | Direct, online quote and buy | Hybrid tool plus consultancy |
| Qdos | Status, human review, cover | £125 + VAT | Direct, insurance led | Clause by clause, written report |
| Markel Tax | Status, human review, cover | Not published | Via accountant or broker | Gateway to Survive35 cover |
Qdos pricing verified against its own product page on 14 August 2026. IR35 Shield publishes no price for its paid legal contract review, which is delivered via a legal partner, and offers a separate free status assessment. Kingsbridge and Markel Tax do not publish contractor pricing for review products. Prices change; check before relying on one.
If you want the review and the liability covered together
Of the three insurance-backed providers, Kingsbridge is the one whose IR35 Protect policy flexes to protect whichever party HMRC holds liable, the contractor or the fee-payer, rather than the contractor alone. That matters where your agency or client could end up carrying the assessment. It bundles unlimited status assessments into its premium tier and quotes online, and it does not publish a starting price, so you will need a quote to compare it against Qdos's £125 plus VAT review.
Get a Kingsbridge IR35 Protect quoteSponsored link. We may earn a referral fee if you take out a policy, at no extra cost to you.
Take-home calculators
These answer the separate question of what each status outcome is worth to you. The single biggest difference between them is the billable days assumption, which moves the answer more than IR35 status does.
| Tool | What it answers | Price | Access | Shows reasoning |
|---|---|---|---|---|
| IR35 Verdict | Three scenarios inc. salary sacrifice | Free | Direct, no account | 220 billable days by default |
| ContractorCalculator | Inside vs outside take-home | Free | Direct | Long established, two scenarios |
| ContractorUK | Inside vs outside take-home | Free | Direct | Two scenarios |
| ir35guide.co.uk | Inside vs outside take-home | Free | Direct | Full limited company model |
Feature descriptions reflect each tool's own published description. We have not audited competitors' arithmetic and do not claim to.
Which one you need depends on the question
Most "best IR35 tool" comparisons rank tools against each other as though they compete. Mostly they do not, because they answer different questions. Sorting by the question you actually have is more useful than sorting by a score.
- "My client says inside and I think they are wrong." You need reasoning you can put in front of them, not another label. Start with a tool that names the factors and the case law, then escalate to a paid human review if the money justifies it.
- "I have been offered a rate to go inside." That is a calculator question. See what rate inside IR35 matches your outside rate.
- "I need to show I took reasonable care." A documented assessment matters more than which tool produced it. A CEST result with its reference number, kept alongside a reasoned second opinion, is a stronger file than either alone.
- "I want the liability covered, not just assessed." No assessment tool does this. That is insurance, and our guide to the three main providers covers who offers what.
Where we are not the right choice
A comparison written by one of the things being compared is worth very little unless it is willing to say this, so plainly:
- If you need an HMRC-facing determination, use CEST. HMRC has said it will stand by a CEST result where the answers were accurate and given in good faith. No third-party tool, including ours, carries that.
- If your case is borderline and the sums are large, pay for a human. Qdos, Kingsbridge and Markel Tax employ specialists, including former HMRC inspectors in Qdos's case. An automated read of a contract does not replace that judgement.
- If you want cover, we do not sell it. We are not an insurer and we are not a regulated adviser.
- If you want a single confident label, we will disappoint you. We report a probability, because that is what the evidence usually supports. Tools that return a definitive answer to a genuinely borderline case are offering certainty they do not have.
What we are good at is the combination: a case law based read of your contract and a three-scenario view of what the outcome is worth, in one place, free, with the arithmetic shown. If that is your question, start with the contract checker.
Frequently asked questions
What is the best IR35 tool?
There is no single best tool, because contractors are not all asking the same question. If you need a status read, CEST, IR35 Shield and our contract checker are free starting points. If you need to know what a determination costs you, that is a calculator question, not a status question. If your case is genuinely borderline or you want an insurance-backed opinion, a paid human review from Qdos, Kingsbridge or Markel Tax is the right answer and no free tool substitutes for it.
Which IR35 tools are free?
HMRC's CEST, IR35 Shield's contractor assessment, and IR35 Verdict's contract scan and calculator are all free. ContractorCalculator, ContractorUK and ir35guide.co.uk publish free take-home calculators. Qdos publishes its full contract review at £125 plus VAT, verified 14 August 2026. Kingsbridge bundles assessments into its IR35 Protect premium tier, and Markel Tax reviews are accessed through an accountant or broker.
Is a free IR35 tool good enough?
For most engagements, a free tool that shows its reasoning will tell you whether your position is comfortable, borderline or weak. That is usually enough to decide what to do next. It is not enough when the answer is borderline and real money turns on it, when you need a documented opinion to show reasonable care, or when you want the liability insured. Those are the cases where a paid human review earns its fee.
What is the difference between an IR35 status tool and an IR35 calculator?
A status tool tells you whether an engagement is likely inside or outside IR35. A calculator tells you what each of those outcomes is worth to you in take-home pay. They answer different questions and neither substitutes for the other. Being told you are inside IR35 without knowing what it costs you leaves you unable to decide whether to negotiate, challenge or accept.
When is IR35 Verdict not the right tool?
When you need a human opinion rather than an automated one, when you need insurance-backed cover against the liability, or when you need a determination you can rely on with HMRC. We do not provide human review, we are not an insurer, and we are not a regulated adviser. For an HMRC-facing determination, run the official CEST tool at gov.uk and keep the reference number.