If you run a personal service company, you've probably seen IR35 insurance offered alongside your accountancy or your professional indemnity cover. The pitch is simple: pay a small annual premium and you're protected if HMRC challenges your status. The reality is more nuanced, because "IR35 insurance" is not one product. It's a label for two quite different things, and buying the wrong one leaves a gap exactly where you thought you were covered.
This guide explains what each type of cover actually pays for, who carries the IR35 risk now that the off-payroll rules have shifted responsibility to many clients, and how to decide what you genuinely need. We've written it for limited company contractors and freelancers who want a clear answer rather than a sales page.
You'll get plain definitions, an illustrative cost example using current tax rates, and a short decision checklist.
What is IR35 insurance, really?
IR35 is the common name for the rules that decide whether a contractor working through their own limited company (a personal service company, or PSC) is genuinely in business on their own account, or whether they're really a disguised employee of the end client. If an engagement is "inside IR35", broadly the same Income Tax and National Insurance should be paid as if the worker were employed.
"IR35 insurance" is cover that helps you deal with the cost and risk of an HMRC challenge to that status. In the market you'll see it sold under names like tax enquiry insurance, tax investigation cover, legal expenses cover, and tax liability cover.
Here's the part that catches people out. Some of these policies only pay for the cost of defending an investigation. Others go further and pay the tax itself if you lose. They are not interchangeable, and the cheap one is usually the first kind.
Tax enquiry cover vs tax liability cover: what's the difference?
There are two layers of protection, and it helps to keep them separate in your head.
Tax enquiry cover (also called tax investigation or fee protection cover) pays for the professional cost of defending you when HMRC opens an enquiry. That means your accountant's or a tax specialist's time spent answering HMRC's questions, preparing correspondence, and representing you. Crucially, it does not pay any tax, interest, or penalties HMRC decides you owe. It only covers the cost of the fight, not the bill at the end of it.
Tax liability cover (sometimes called IR35 protection) is broader. As well as the defence cost, it can pay the additional tax, interest, and penalties if HMRC successfully argues the engagement was inside IR35. This is the cover most people picture when they imagine being "insured against IR35", and it is more expensive and more conditional.
The table below shows the practical difference.
| Feature | Tax enquiry cover | Tax liability cover |
|---|---|---|
| Pays for accountant or specialist representation during an enquiry | Yes | Yes |
| Covers IR35-specific status arguments | Usually, if IR35 is included | Yes |
| Pays the additional tax if you're found inside IR35 | No | Yes, up to the policy limit |
| Pays interest and penalties | No | Often, subject to terms |
| Typical relative premium | Lower | Higher |
| Usually requires a status review or risk assessment | Not always | Commonly |
Many accountancy firms include basic tax enquiry cover as standard, which is genuinely useful. But it's easy to assume that "included cover" means you're protected against an IR35 bill, when in fact it only funds the defence. Read the schedule, not the headline.
Who actually carries the IR35 risk now?
This is the question that decides whether the cover is worth buying at all, because the off-payroll working rules changed who is responsible for getting the status decision right.
Under the off-payroll working rules, responsibility depends on the end client.
- Public sector clients have had to determine a contractor's status since 2017.
- Medium and large private sector clients have had to determine status since the rules changed on 6 April 2021.
- Small clients outside the public sector are the exception. Here, the worker's own intermediary, your PSC, is still responsible for deciding whether the rules apply and for accounting for any tax due.
Where the client is responsible, it must issue a Status Determination Statement (SDS) explaining its decision and the reasons for it. When a medium or large client gets that decision wrong, the tax risk generally sits up the supply chain with the fee-payer or client, not with you.
That sounds like contractors are off the hook. Two things stop that being the full picture.
First, if you work for small clients, the risk is still entirely yours. A small client is currently one that does not meet at least two of three tests: turnover over £10.2 million, balance sheet total over £5.1 million, and more than 50 employees. The thresholds were raised under the Companies Act size rules from 6 April 2025 (to £15 million turnover and £7.5 million balance sheet, with the 50-employee test unchanged). Because a client's size is judged on accounts already filed before the tax year starts, HMRC's own guidance is that this increase does not feed into off-payroll status decisions until the 2027/28 tax year at the earliest. When it does bite, the practical effect is that more clients will count as small, which pushes the determination, and the risk, back onto more contractors.
Second, the rules apply per engagement. You might have one outside-IR35 contract with a small start-up where you carry the risk, and another with a large bank where the bank carries it. Cover decisions should follow your actual contract mix, not a blanket assumption.
If you want to confirm where you stand on a given contract, HMRC publishes the Check Employment Status for Tax (CEST) tool, and a proper status review from an adviser carries more weight than a gut feeling. Our IR35 contractor accounting service exists to keep those determinations defensible.
What could an inside-IR35 finding actually cost?
The reason tax liability cover exists is that a successful IR35 challenge can be expensive, especially across several open years. The figures below are illustrative only and use 2025/26 rates to show how the arithmetic works. They are not a quote and your own position will differ.
Illustrative example
Priya runs a PSC and takes a typical small salary plus dividends. On one engagement with a small client, she draws £50,000 from the company for the year: £12,570 as salary and £37,430 as dividends. Because she manages her own status, the IR35 risk on this contract is hers.
As a rough comparison of the personal tax treatments:
- Outside IR35, taken as dividends. The first £12,570 salary is covered by the personal allowance for 2025/26. Of the £37,430 in dividends, £500 is within the dividend allowance, leaving £36,930 taxable. All of it falls in the basic rate band, taxed at the 8.75% dividend ordinary rate, which is about £3,231 of dividend tax for the year.
- Inside IR35, treated like employment income. The same £50,000 would broadly be subject to Income Tax at 20% and employee National Insurance at 8% on earnings above the relevant thresholds, plus employer National Insurance at 15% would apply within the deemed payment calculation. The combined effect is materially higher than the dividend route, and HMRC can add interest and penalties on top across each open year.
The exact reassessment depends on the deemed payment calculation, the years in scope, and any offsets, so we have not put a single headline number on it. The point is simply that the gap between the two treatments, multiplied across several years and topped with interest and penalties, is what a tax liability policy is designed to absorb. If you want to model your own take-home under each route, our take-home pay calculator and dividend tax calculator are a sensible starting point.
Do you need IR35 insurance at all?
Not every contractor needs the same level of cover. Run through these questions before you buy.
- Do you work for any small or public sector clients where you, or your PSC, determine status? If yes, you carry real IR35 risk and tax liability cover is worth serious thought. If all your clients are medium or large private sector firms issuing an SDS, the headline IR35 tax risk usually sits with them, though enquiry cover is still useful.
- Could you absorb the professional cost of a multi-month HMRC enquiry yourself? Defending an enquiry can run to thousands of pounds in adviser time even if you ultimately win. Tax enquiry cover exists precisely for this.
- Have your contracts been status-reviewed, or are you relying on hope? Insurers usually want evidence that you've taken reasonable care, and a documented review both reduces your risk and tends to be a condition of the better policies.
- Does your accountant already include enquiry cover? Many do. Confirm whether it extends to IR35 status arguments and whether it pays only defence costs or tax too.
If you answer "small client", "no I couldn't easily absorb it", and "no I haven't had a review" to the first three, the case for proper cover is strong. If your work is exclusively with large clients who handle determinations, you may decide enquiry cover alone is proportionate.
How to choose the right policy
Once you know which layer you need, the detail matters more than the brand.
- Check exactly what's paid. Defence costs only, or tax, interest, and penalties too? This is the single most important line in the schedule.
- Check the indemnity limit. A limit that looks generous can still fall short across several open years. Match it to your contract values and how long you've been trading.
- Check the conditions precedent. Many liability policies only pay out if your contracts were status-reviewed before the enquiry and you took reasonable care. A policy you've technically breached pays nothing.
- Check whether IR35 is actually included. Some general tax enquiry policies exclude or limit IR35 status disputes. Do not assume it's in there.
- Check retrospective cover. An enquiry can reach back over earlier years. Understand whether past contracts are covered or only new ones.
The cover is only as good as the status position behind it. The most reliable protection is getting determinations right in the first place, keeping the evidence, and reviewing contracts before you sign. That's the work our contractor accountants and tax advisory team do day to day.
Want to know whether your contracts leave you carrying IR35 risk, and what cover actually fits? Book a free 20-minute call with a Zmartly accountant and we'll review your contract mix and your options.
Frequently asked questions
Is IR35 insurance worth it?
It depends on who your clients are. If you work for small or public sector clients where your own company decides status, you carry the IR35 tax risk and liability cover can be worth it. If you only work for medium and large private sector clients that issue a Status Determination Statement, the headline tax risk usually sits with them, though enquiry cover to fund a defence is still sensible.
What is the difference between tax enquiry cover and tax liability cover?
Tax enquiry cover pays the professional cost of defending an HMRC investigation, such as your accountant's or a specialist's time. It does not pay any tax you're found to owe. Tax liability cover goes further and can pay the additional tax, interest, and penalties if HMRC decides an engagement was inside IR35, up to the policy limit.
Who is responsible for IR35 since the off-payroll rules changed?
Public sector clients have determined status since 2017, and medium and large private sector clients since 6 April 2021. For small clients outside the public sector, the worker's own intermediary, the PSC, is still responsible for deciding whether the rules apply and accounting for any tax due.
Does IR35 insurance cover other HMRC investigations?
Often, yes. IR35 cover is frequently sold within a wider tax enquiry or fee protection policy that can also respond to VAT, PAYE, and Self Assessment enquiries. Always check the schedule to confirm which taxes and which type of dispute are included.
Will my accountant's enquiry cover protect me against an IR35 tax bill?
Usually not on its own. Many accountancy firms include tax enquiry cover that funds the defence of an investigation but does not pay the tax, interest, or penalties if you lose. Check whether IR35 status arguments are included and whether the policy pays only defence costs or the liability as well.
