What Does Inside IR35 Mean for Your Take-Home Pay?

Inside IR35 is not a grey area. It is a verdict, and it lands like one: HMRC decides you are, to all practical purposes, an employee, then taxes you accordingly while your client keeps you off the payroll entirely.

If you have just been told a contract is "inside IR35" and are trying to work out what that actually means for the money in your bank account, this post will give you the concrete numbers, not the vague warnings.

The Definition Nobody Explains Clearly

The rules themselves date from 2000, when Gordon Brown's government introduced IR35 to tackle what HMRC called disguised employment. The idea was simple: if you would have been an employee but for the existence of your limited company, you should pay tax like one. The principle sounds reasonable until you realise that HMRC's own tool for determining status, Check Employment Status for Tax (CEST), has been criticised in two separate House of Lords reports for being inaccurate in genuinely ambiguous cases.

Since April 2021, the responsibility for making that determination shifted from the contractor to the end client, for medium and large businesses. Small clients (under two of the following: 50 employees, £10.2m turnover, £5.1m balance sheet) still leave it to the contractor's personal service company. The result is that many large engagements are now blanket-determined as inside IR35 because it is cheaper for the client to be cautious than to conduct a proper case-by-case review.

What Inside IR35 Actually Does to Your Money

Here is a concrete example. You are a freelance IT consultant contracting through your limited company at a rate that produces £60,000 in annual income. Outside IR35, you would typically pay yourself a small salary (around £12,570, the personal allowance threshold) and take the rest as dividends, which are taxed at 8.75% for basic rate taxpayers rather than 20% or 40% income tax.

Once a contract is inside IR35, your limited company must operate a "deemed salary" calculation. The fee you receive goes through PAYE. You pay income tax at 20% or 40%, employee National Insurance at 8% (dropping to 2% above £50,270), and your client or agency deducts employer National Insurance at 13.8% before paying you, even if they never officially call you an employee.

On £60,000, the employer National Insurance alone accounts for roughly £7,000 that reduces your net pay before you have considered income tax. The dividend route, which might have left you with around £48,000 net outside IR35, now yields closer to £36,000 to £38,000 inside it. That is a real-world gap of £10,000 to £12,000 per year, on the same gross contract value, doing the same work, for the same client.

For a more detailed breakdown of how the pay difference compounds, see Inside IR35 Meaning: What It Actually Does to Your Pay.

The "Employee in Name Only" Problem

Here is the part that should make you genuinely angry: inside IR35 makes you pay like an employee without giving you the rights of one.

Employees are entitled to statutory sick pay, paid holiday (5.6 weeks minimum under the Working Time Regulations 1998), protection from unfair dismissal after two years, redundancy pay, and pension auto-enrolment. Contractors inside IR35 receive none of these automatically. Your client can end the engagement with whatever notice the contract specifies, often four weeks or less, and owes you nothing beyond that.

You still pay employer National Insurance, routed through the fee-payer (your agency or client). But HMRC does not require the client to provide you with anything in return for that 13.8% contribution. It goes to HMRC, not to fund your rights.

This is not a quirk or an oversight. It is the structural design of the legislation. The Court of Appeal acknowledged the anomaly in Pimlico Plumbers v Smith (2017), a case about employment status that illustrated how the employment rights framework and the tax framework can reach different conclusions about the same relationship. IR35 does not grant you employment rights even if it decides you look like an employee for tax purposes.

Why Your Day Rate May Already Have Been Cut

When clients became liable for status determinations in April 2021, many organisations did something economically logical: they increased the contractor's gross rate to offset the employer National Insurance they would now bear. Fewer did this than should have. More quietly reduced day rates to absorb their new liability.

If you are renegotiating a contract or pricing a new one inside IR35, factor in the employer National Insurance as a cost your client is carrying. A contractor genuinely worth £500 per day outside IR35 should be quoting something closer to £570 to £580 per day inside IR35, just to land in the same net position. Many contractors do not have that negotiating power, particularly when agencies act as intermediaries and clip a margin in between.

For the comparison between inside and outside status from a rate-setting perspective, Inside vs Outside IR35: The Decision That Splits Contractors covers the strategic framing in detail.

Can You Challenge a Status Determination?

Yes, and you have a legal right to do so. Since the 2021 reforms, end clients must issue a Status Determination Statement (SDS) if they conclude you are inside IR35. You can formally disagree with that determination, and the client must respond within 45 days. If they fail to do so, liability for the tax shifts back to them.

In practice, many contractors are reluctant to challenge because they fear losing the engagement. That is a rational concern. But if your contract genuinely exhibits the hallmarks of outside IR35 status, principally the right of substitution (you can send someone else to do the work), lack of mutuality of obligation (neither party is obliged to offer or accept work), and control (you decide how the work is done), then a well-evidenced challenge supported by a specialist employment status lawyer or a firm like Qdos Contractor or IR35 Shield is worth pursuing.

HMRC's CEST tool is a reasonable starting point but not the final word. Two separate Lords committees have noted that CEST does not consider mutuality of obligation, which is one of the three primary tests courts use. An "indeterminate" CEST result does not mean you are inside; it means the tool could not decide, which is different.

The MTD Dimension: What Happens If You Have Mixed Income

This is where IR35 and Making Tax Digital start to interact in ways most contractors have not thought through.

If you are inside IR35 and your entire income flows through PAYE, your tax is handled by the fee-payer and you may not meet the MTD for Income Tax threshold (currently set at £50,000 from April 2026, dropping to £30,000 in April 2027). But many contractors have mixed income: some PAYE from inside IR35 engagements, some self-employed income from smaller clients, and possibly rental income on top.

Under MTD for Income Tax Self Assessment (MTD ITSA), once your combined qualifying income exceeds the threshold, you must keep digital records and submit quarterly updates to HMRC. PAYE income does not count toward the MTD threshold, but self-employed and property income does. So a contractor with £30,000 of outside IR35 self-employed income and £40,000 of inside IR35 PAYE income would be MTD-liable from April 2027, needing compliant software for the self-employed portion only.

If you are approaching that territory, understanding what MTD actually requires in practice is worth doing now rather than in a scramble next spring. Tax App for Self Employed: What Changes After April 2026 explains the practical timeline.

The Sole Trader Alternative

Not every contractor operates through a limited company. If you are a sole trader doing project-based work, IR35 does not apply to you in the same way, because there is no intermediary company between you and your client. You already pay income tax and National Insurance on your earnings via Self Assessment.

This is one reason some contractors, particularly those with only one or two clients, have wound down their limited companies since 2021 and returned to sole trader status. The administrative simplicity can outweigh the modest tax advantages that remain when most income is inside IR35 anyway.

The tradeoff is that sole traders have unlimited personal liability and cannot access the flat-rate VAT scheme in the same way. But for a tradesperson or freelancer whose work is clearly self-employed in nature, the sole trader route also sidesteps IR35 entirely, which is its own form of relief.

What "Inside IR35" Means in Plain English

To answer the question this post started with: inside IR35 means HMRC has decided that you are, in substance, an employee of your client, and it is going to tax you accordingly. You will pay income tax and National Insurance as an employee does. Your client will also pay employer National Insurance on your earnings, which reduces the net rate they can offer you. You will not receive employment rights in return.

If the determination is wrong, you can challenge it. If it is right, you can accept it, adjust your rates to compensate, or restructure how you work. What you cannot do is ignore it: since April 2021, the fee-payer bears the liability if they fail to deduct correctly, which means agencies and clients are highly motivated to enforce compliance.

For most contractors, the decision to accept or fight an inside IR35 determination is the most consequential financial choice they make each year. Running the numbers properly, ideally with a tax specialist who knows IR35 case law rather than just the CEST tool, is worth every penny of that advice fee.

You started reading this post because someone told you a contract was inside IR35 and you were not sure what that meant. Now you know: it means your take-home pay just got significantly smaller, and the person who made that determination probably did not have to justify it to anyone.