IR35 is one of the most tricky rules of HMRC and most business owners never understand them and end up paying penalties to HMRC. If you are a contractor through a limited company or a business hiring contractors you will always feel anxiety hearing IR35. 

This guide will explain how IR35 legislation works, who it affects, and how to stay compliant without overcomplicating things.

What is IR35?

Inland Revenue 35, such as IR 35 is a UK implemented legislation, also referred as off-pay working rules that helps identify contractors are really self employed or disguised employees.

IR35 applies both on private sector and public sector and helps Government determines whether the contractor who is enjoying the benefits of an business owner is really self employed and not betraying HMRC and saving income tax & national insurance.

Businesses that are exempted from IR35:

Small businesses which follow 2 of the following criteria are exempted:

  • Gross assets of less than 5.1 million on the balance sheet
  • Less than 10.1 million annual turnover
  • Less than 50 employees

Categories of IR35 Status

In the IR35 legislation, the companies are subjected to decide the IR35 status of their contractors in the contract of employment.

The IR35 legislation divides the contractors into 

  1. Inside IR35
  2. Outside IR35

Who are outside IR35?

If a contractor is classified as an independent business owner and not an employee then he has the status “outside IR35”

Now he can pay himself a salary, take dividends and can pay taxes through a limited company.

In both public and private sector, the client is responsible for determining the outside IR35 status but still it can be investigated by HMRC.

Who is “inside IR35”?

If a contractor is inside IR35 then it means he has to pay taxes and national insurances as a full time employee. (The contractors works separately but the criteria for outside IR35 is not fulfilled)

This means no business owner benefits, can’t take dividends and no sick or holiday pay and PAYE tax must apply.

For these contractors, the client issues a “deemed payment” at the end of tax year. If the contractor has changed his status then the HMRC investigates again.

Who are affected by IR35 rules?

You may be affected by IR35 rules if you are:

  • A contractor/worker providing services through your own intermediary, usually a limited company or Personal Service Company (PSC).
  • A client hiring a contractor through their intermediary.
  • An agency or supplier providing contractors’ services through an intermediary.

Note: The rules can vary depending on the size of the client. Small businesses have slightly different responsibilities than medium or large organisations.

When Do the IR35 Rules Apply?

IR35 rules come into play when:

  • A worker provides services through their own intermediary rather than being hired directly.
  • The responsibility for deciding IR35 status depends on the type of client:
    • Public sector or medium/large private sector: the client decides whether the contractor falls inside or outside IR35.
    • Small private businesses: the contractor’s own intermediary decides their IR35 status.
  • Agencies always have some responsibility under the rules, especially when they are treated as the deemed employer.

Quick Real-Life Example: When a Contractor Quietly Becomes an Employee

A founder believed they were safe using a contractor because there was no employment contract in place. The contractor invoiced monthly, worked on key projects, and had supported the business for years.

Over time, the work became ongoing and closely tied to day-to-day operations. The business relied heavily on the individual, and the arrangement shifted from project-based work to open-ended, time-based support.

While this felt normal and unintentional, HMRC looks beyond labels. When continuity, reliance, and control build up, a contractor can start to look like an employee.

The lesson is simple: contracts must reflect how the work is meant to operate. Outcome-led, independent arrangements reduce the risk long before HMRC asks questions.

How Does an SDS Help Companies Comply with IR35 Rules?

An SDS (Status Determination Statement) must be issued by the companies that clarify whether the contractor is inside IR35 or outside IR35. It starts from the end client who is receiving services then to an agency and then to the contractor’s limited company or personal service company and finally to the individual contractor.

An SDS is not just a document from the company. It needs to provide clear evidence about how the client came to this conclusion and provide all the available reasons to show HMRC that the reasonable care is taken and the decision is correct. If the situation changes after sometime then another SDS needs to be issued.

What Happens If a Contractor Disagrees With the SDS?

The SDS is not a final verdict The contractor can disagree and challenge verbally or in written form within 45 days and once the company receives the dispute, the clock start ticking

The company then has 45 days to respond back. The company can either stand firm on their decision and provide written evidence of their decision or change the SDS. If the company fails to issue an SDS within 45 days then the responsibility of the income tax and NIC of the contractor falls on the company.

What Does “Reasonable Care” Mean Under IR35?

Reasonable care means that the company makes an effort to properly investigate the contractor status and give relevant proof about their decision. This reasonable care satisfies the contractor and HMRC as well.

This usually involves asking practical questions, such as whether the contractor has other clients, whether they take on financial risk, and how independent they are in reality. Companies should also look closely at actual working practices and compare them with those of permanent employees. If a contractor works in the same way as staff, that detail matters.

By collecting this information, documenting the reasoning behind the decision, and keeping proper records, companies demonstrate that they have taken IR35 seriously. If the decision is taken randomly without following any reasonable care then this can attract HMRC scrutiny.

How to Pay Contractors and Stay Compliant in the UK After IR35

IR35 is not here to discourage contracting work in the UK It was introduced to remove the tax loopholes and help HMRC collect the right rates of taxes. IR35 is here to help the government not to stop skilled professionals in the UK from working.

By understanding IR35, issuing accurate SDSs, and maintaining clear documentation, companies can continue to engage contractors with confidence. 

What Are Umbrella Companies and How Do They Fit Into IR35?

An umbrella company handles the tax and payroll of the contractor and sits between the contractor and the end client. The contractor is employed under the umbrella company and follows inside IR35 for tax purposes.

While umbrella companies can simplify administration, they have also been linked to non-compliant pay arrangements in the past. This has forced HMRC to apply new rules across the supply chain for better compliance.

What’s Changing for Umbrella Companies in 2026?

From April 2026, responsibility for unpaid PAYE tax and National Insurance will no longer sit only with the umbrella company. From April 2026, the unpaid tax will be recovered from the recruitment agency and the client. This rule will shift accountability across the supply chain and the agencies and clients will be selective when hiring umbrella companies.

These updates are designed to reduce tax avoidance and clean up the umbrella market. As a result, agencies and clients are becoming far more selective, often limiting which umbrellas contractors can use or moving workers onto direct PAYE models instead.

What This Means for Contractors and Businesses

For contractors, these changes should lead to more transparency and fewer risky pay arrangements. For businesses and agencies, they increase the importance of due diligence and record-keeping. Umbrella companies will continue to operate, but the days of treating them as a risk-free solution are coming to an end.

How can Reflex accounting help you with IR35?

Reflex accounting has an efficient team that can remove all the stress of deciding whether the contractor falls inside IR35 or outside IR35. We can review the contract and working practices to help you make the final decision. On the other hand, we also help contractors inside IR35 to know which company structure is best for them and handle their income tax and National insurance so the contractor remains compliant to HMRC and minimizes administrative hassle.

If the contractor falls outside IR35 then we provide all the accounting services like corporation tax returns, VAT, Director salary & dividend calculation so they remain compliant and get the maximum financial benefits as an independent contractor.

If you need Reflex accounting to handle your finances then contact us now.

FAQs

Does Inside IR35 Status Turn a Contractor into an Employee?

No. Inside IR35 means you’re taxed like an employee, not treated as one. You usually won’t get employee benefits such as holiday pay or job security.

How Is IR35 Status Determined?

HMRC looks at how you actually work, not just the contract. Control, substitution, and day-to-day working practices are the key factors.

Is the Healthcare Sector Most Affected by IR35?

Healthcare has been heavily impacted, especially in the NHS, but IR35 affects many sectors where contractors are widely used.

Are Locum Doctors More Likely to Be Inside or Outside IR35?

Many locum doctors fall inside IR35 due to the nature of NHS roles, but each contract is assessed individually.

What Does “Inside IR35” Mean for My Take-Home Pay?

You’re paid through PAYE, so tax and National Insurance are higher. This usually reduces take-home pay compared to working outside IR35.

Can I Challenge My IR35 Determination if I Disagree?

Yes. You can formally dispute the decision, and the client must review and respond within 45 days.