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What IR35 actually is

IR35, formally the off-payroll working rules, exists to stop people working like employees while being paid through a limited company to reduce tax. If HMRC considers that, stripped of the company in the middle, you look like an employee of your client, your engagement is inside IR35 and is taxed broadly like employment. If you genuinely operate as a business providing services, you are outside IR35 and taxed accordingly. The difference in take-home pay between the two can be substantial, which is why getting it right matters.

Status is not decided by your job title or your contract heading. It is decided by the substance of the arrangement, judged against decades of employment case law.

Who decides your status in 2026

This is where many contractors get caught out, because the answer depends on the size of your client.

For medium and large clients in both the public and private sectors, the client is responsible for determining your status and must issue a Status Determination Statement. Where you work through an agency, the fee-payer in the chain then operates the appropriate deductions if you are inside.

For small clients, responsibility sits with you, the contractor, through your own company, under the original chapter of the IR35 rules. That distinction, who counts as small, is precisely what moved in April 2026.

What changed in April 2026

From 6 April 2026, the thresholds that define a small company were raised, which means more clients now qualify as small. When your client is small, the responsibility for determining and accounting for your IR35 status returns to you rather than sitting with the client. In practical terms, a group of contractors who had handed responsibility to their clients found it landing back on their own shoulders.

Two points temper that. Company size is judged over two consecutive financial years, so a client does not flip from medium to small overnight, and the full effect of the change feeds through over time rather than all at once. And being responsible for your own status is not the same as being inside IR35. It simply means the determination, and the risk of getting it wrong, sits with you again.

We cover the detail, including who is affected and what to do about it, in our dedicated guide to the April 2026 IR35 threshold changes. If the change affects you, that is the piece to read next.

The other big 2026 change: umbrella companies

The threshold shift grabbed the headlines, but for anyone working inside IR35 through an umbrella company, a second change from 6 April 2026 matters just as much. New rules make others in the labour supply chain jointly and severally liable for the PAYE and National Insurance due on umbrella workers' pay. The umbrella company is still the primary employer for tax, but if it fails to hand the correct tax to HMRC, HMRC can now pursue another party for the shortfall. In most chains that party is the recruitment agency sitting closest to the end client. Where there is no UK agency, it is the end client.

The aim is to clean up a market that has long had a non-compliance problem. For you as a contractor, the practical effects are indirect but real. Agencies and clients now have a strong incentive to vet umbrellas carefully, so you may find your client or agency restricting which umbrellas you can use, or moving you onto an approved list. It also makes it more important than ever to use a compliant umbrella, because a chain that collapses is disruptive even when the liability does not land on you. This is a compliance measure rather than full regulation of the umbrella market, with broader umbrella regulation expected separately from 2027.

One related cost worth knowing: employer's National Insurance, which inside-IR35 umbrella workers effectively fund out of their assignment rate, rose to 15% from April 2025, with the threshold at which it starts cut to £5,000. That has quietly widened the gap between inside and outside take-home, and it is part of why mitigation such as a salary sacrifice pension now matters more.

The case law that decides inside or outside

Whoever makes the determination, they are applying the same body of law. Four cases do most of the heavy lifting in 2026, and it is worth knowing how they fit together.

Ready Mixed Concrete (1968) sets the framework: three conditions, personal service, control, and a wider arrangement consistent with employment, that a tribunal works through. Autoclenz (2011) established that what you actually do outweighs what the contract says where the two diverge. PGMOL (2024) lowered the bar on mutuality of obligation, weakening a defence many contractors relied on. Atholl House, the Kaye Adams case, confirmed that being genuinely in business on your own account, with multiple clients and real independence, is the decisive battleground.

Read together, the direction of travel is clear. The old technical defences, unused substitution clauses and no-mutuality arguments, have weakened. The strong position in 2026 is being able to show you genuinely operate as a business. If you want to go deeper on any of these, our explainers on mutuality of obligation and the PGMOL ruling are good places to start.

A note on CEST

You may be asked to use HMRC's CEST tool, or your client may use it to determine your status. It is worth knowing its limits. CEST produces a binary result with no reasoning, struggles with mutuality of obligation, and takes the answers it is given at face value rather than testing them against reality. It is one input, not the final word. Our guide on whether CEST is accurate explains where it can diverge from what a tribunal would find.

Where this leaves you in 2026

The headline for 2026 is continuity with a sting in the tail. The fundamental test has not changed, but the April threshold shift has put more contractors back in charge of their own status, the umbrella reforms have tightened the supply chain around inside-IR35 work, and the recent case law has made the genuine in-business picture more important than ever. The contractors in the strongest position are the ones who understand where they stand before anyone asks them to prove it.

If you want a concrete sense of what status means for your pay, you can model the take-home difference between inside and outside for your own day rate using our free take-home calculator.

This guide is general information to help you understand the rules. It is not legal or tax advice. For your own circumstances, speak to a qualified contractor accountant.

Frequently asked questions

What are the IR35 rules in 2026? IR35, or the off-payroll working rules, decide whether a contractor working through their own company is treated as genuinely self-employed (outside IR35) or like an employee for tax (inside IR35). The 2026 position is largely the same test as before, but the April 2026 threshold change moved more contractors back to being responsible for their own status.

Who decides my IR35 status in 2026? For medium and large clients, the client decides and issues a Status Determination Statement. For small clients, you decide through your own company. The April 2026 threshold change increased the number of clients counted as small.

What changed for IR35 in April 2026? The thresholds defining a small company rose from 6 April 2026, so more clients now qualify as small. When your client is small, responsibility for your IR35 status returns to you rather than the client.

What are the umbrella company changes from April 2026? From 6 April 2026, parties higher up the labour supply chain, usually the recruitment agency closest to the end client, can be held jointly and severally liable for unpaid PAYE and National Insurance on umbrella workers' pay. The umbrella remains the primary employer for tax. For contractors the effects are indirect: expect agencies and clients to vet umbrellas more tightly and possibly limit which umbrellas you can use.

Is CEST reliable for checking IR35 status in 2026? CEST is a useful starting point but has well-known limits. It gives a binary result with no reasoning, handles mutuality of obligation poorly, and accepts your answers at face value. It is best treated as one input rather than a definitive answer.

IR35 Verdict helps you understand your IR35 position. It does not provide legal or tax advice. Always consult a qualified contractor accountant before making decisions about your status.