The Outside-IR35 Comeback: What Has to Come Back With It

Introduction

Four years after blanket inside-IR35 policies cleared out contractor populations across UK plc, the conversation is shifting. ContractorUK asked in December whether 2026 would see the return of the outside-IR35 contractor. Bauer & Cottrell argued in April that the new umbrella joint and several liability regime has, perversely, made outside-IR35 engagement less risky for end clients. Right-of-substitution explainers are back in circulation as day-rate markets tighten and project owners look at the contractor talent they lost.

This is a reasonable moment to look again. It is not a reasonable moment to reopen outside-IR35 engagement without knowing, concretely, who you currently engage and under what basis. This post sets out what has genuinely changed, what a credible outside-IR35 engagement looks like in 2026/27, and the visibility work that has to happen before any policy reopens.

Why the conversation is reopening now

Three things moved at once.

The first is the JSL regime. From 6 April, end clients and agencies share joint liability for umbrella PAYE. That raises the cost of the defensive route, the one where engagers pushed contractors through umbrellas primarily to insulate themselves from IR35 exposure. If the umbrella route is now carrying more of its own risk, the relative penalty for engaging a limited-company contractor outside IR35 has narrowed.

The second is the rate market. Four years of blanket bans did what blanket bans do. The contractors who had options went to engagers who would still treat them as contractors. Project rates have drifted and delivery timelines have slipped in functions that depended on specialist interim work. Heads of Engineering, Tax and Transformation are making the case internally that the policy cost more than it protected.

The third is case law. Tribunals in 2025 and early 2026 have continued to turn on behaviour as well as contract wording. The Ascend Payroll review of five recent decisions is a useful read here. Judges are looking at whether the worker had a genuine right of substitution, whether the engager exercised day-to-day control, and whether there was mutuality of obligation in practice. "Mutuality of obligation" is the expectation that work will be offered and accepted on an ongoing basis, the way it is for an employee. Contracts that describe a contractor relationship but document an employee one continue to lose.

The combined effect is that outside-IR35 engagement is more defensible in 2026 than it was in 2022, provided the engagement is genuine. That is the important qualifier.

What a credible outside-IR35 engagement looks like now

Three tests still decide the question.

Right of substitution is the first. Can the contractor send someone else in their place to do the work, and would you accept them if they did? ContractorUK's February explainer positions substitution as the strongest single indicator for 2026/27, and tribunals agree. An unfettered right in the contract that the engager would never actually honour is worth very little. A genuine right, used occasionally, is worth a lot.

Control is the second. Who decides what is done, how it is done, when and where? An outside-IR35 contractor is engaged to deliver a specified outcome. If your line managers supervise the work the way they supervise employees, the engagement is inside regardless of what the contract says.

Mutuality of obligation is the third. Is the engager obliged to offer continuing work, and is the contractor obliged to accept it? Rolling contracts that renew automatically for years, with the contractor integrated into the team and expected to take on whatever comes up, start to look like employment.

None of this is new advice. What is new is that the regulatory and market environment now rewards engagers who can evidence the behaviour, not just the paperwork. Status Determination Statements produced at the start of an engagement are necessary but nowhere near sufficient. The defence sits in what actually happened over the life of the contract.

The infrastructure required before reopening

Here is where most reopening conversations go wrong.

A policy review does not tell you who you currently engage. It tells you what your policy says. Those are different documents. In the organisations we talk to, the gap between the two is usually 20 to 60 per cent. Finance has a view from purchase orders. HR has a view of badged workers. Procurement has a view of supplier contracts. Line managers have a spreadsheet. None of these lists agree.

Before a blanket inside-IR35 policy is softened, three things need to exist:

A live register of the external workforce. Every individual delivering services to the organisation, regardless of the contracting vehicle, with their engagement basis, start date, end date, paying entity and hiring manager. It is also the list you need before you can make any policy decision that differentiates between engagement types.

A classification audit trail. For every engagement, the determination made, the evidence it was based on, and a record of any behavioural checks during the engagement. The Post Office case is instructive. A £104 million HMRC bill, reported in March, with the Post Office declining to use the IR35 offset. One of the largest single bills HMRC has issued under the off-payroll rules. The exposure built up over years of engagements where determination and practice drifted apart. Nobody was watching the drift.

Change controls. A mechanism that flags when an engagement materially changes. The contractor who starts on a defined project and ends up running business-as-usual work two years later has, in substance, moved inside IR35 regardless of the original determination. Without a change control, the paperwork and the behaviour diverge quietly and the exposure compounds.

Reopening outside-IR35 engagement without these three is not a policy decision. It is a bet that HMRC and the Fair Work Agency will not look too closely. It is a bad one in 2026.

A sequenced approach

The reopening conversation lands better in this order.

First, build the register. Get finance, HR, procurement and hiring managers onto one list of who is currently engaged and on what basis. Reconcile it. Understand the gaps before assuming they are small.

Second, review the policy against the register you now have. Blanket inside-IR35 decisions were made in 2020 and 2021 in the absence of good data. Look at the engagements individually. Where is the genuine project work? Where is the disguised business-as-usual? Where are the PSCs you already have that could defensibly sit outside?

Third, reopen selectively. Pilot outside-IR35 engagement in the functions where substitution, control and mutuality genuinely point that way. Instrument the behaviour through the engagement, not just at the start. Make the classification defensible by how the work is actually run.

This is how successful organisations came back to mixed-engagement models without the exposure. The register came first. The policy followed the data. The engagement followed the policy.

Key Takeaways

• The outside-IR35 conversation is reopening for real reasons: JSL, market rates, and a clearer case-law picture. Acting on it without visibility is still a bad idea.
• Substance beats paper. Substitution, control and mutuality of obligation determine correst status, not contract clauses or CEST outputs.
• The infrastructure you need before reopening policy is a live register of external workers, a classification audit trail, and change controls for in-flight engagements.
• Post Office's £104 million HMRC bill shows what happens when determination and practice drift apart over years without anyone watching.

What This Means for Your Organisation

Reopening outside-IR35 engagement is a reasonable 2026 decision. Reopening it without a current register of your external workforce is not. Start with the list, not the policy.

If you want a sense of how accurate your current view is, CoComply helps CFOs, Heads of Tax and People leaders build a single picture of the external workforce so that classification decisions rest on what is actually happening, not what was documented two years ago.

Sources:

• ContractorUK, "Will 2026 see the return of the 'Outside IR35' contractor?" (Dec 2025): https://www.contractoruk.com/news/will-2026-see-return-outside-ir35-contractor
• ContractorUK, "How key will Right of Substitution be for IR35 in 2026/27?" (24 Feb 2026): https://www.contractoruk.com/ir35-reading/ir35-right-to-substitution-202627-explainer
• Bauer & Cottrell, "Umbrella JSL rules just made IR35 less risky" (Apr 2026): https://www.bauerandcottrell.co.uk/2026/04/umbrella-jsl-rules-just-made-ir35-less-risky/
• Ascend Payroll, "IR35 in the courts — five recent tribunal decisions" (24 Mar 2026): https://ascendpayroll.co.uk/ir35-in-the-courts-what-five-recent-tribunal-decisions-mean-for-your-business/
• ContractorUK, "Post Office won't use IR35 offset despite £104m HMRC bill" (Mar 2026): https://www.contractoruk.com/news/post-office-wont-use-ir35-offset-despite-biggest-ever-104m-hmrc-bill