Guides · Updated 13 October 2026

IR35 for locums. When it applies, and who decides.

IR35 is the name most people use for the off-payroll working rules. They matter if you locum through your own limited company. If you work as a sole trader they do not apply in the same way, though your employment status still matters.

A healthcare worker in uniform standing in a corridor

What the rules are for

The off-payroll working rules make sure that someone working through their own company pays broadly the same Income Tax and National Insurance as an employee would, where the job is really employment in all but name.

When they apply

They apply if you provide your services through your own intermediary, usually a limited company, and you would have been an employee if you had been engaged directly. Whether that is true is decided booking by booking, on the facts of how you work.

Who decides

It depends on the size of the client. For medium and large clients, and for public bodies, the client decides your status and must tell you. For small clients in the private sector, your own company makes the decision. Many independent practices are small businesses, while large chains and NHS bodies are not, so a locum can meet both in the same month.

Example: Two bookings in the same month

A small independent workplace: Your own company decides whether the rules apply
A large chain or an NHS body: The client decides, and tells you what it decided

Both are through your own limited company. The work can be identical and the process still differs.

Checking your status

HMRC has a tool called Check Employment Status for Tax. It asks about the booking and gives a view on whether it looks like employment. HMRC says it will stand by the result as long as the information you gave was accurate.

What to keep

Keep the terms of each booking: who engaged you, what was agreed and any status decision you were given. If your status is ever questioned, that record is what you will be asked for.

Inside and outside

A booking is called "inside IR35" when it is treated as employment for tax, and "outside" when it is not. Inside means tax and National Insurance are taken before the money reaches your company.

One booking at a time

The rules apply contract by contract. Being outside for one client says nothing about the next, so each new arrangement is looked at on its own facts.

Agencies and umbrella companies

If an agency sits between you and the client, it has duties in the chain too. Some locums are offered an umbrella company instead, where you become its employee and are paid through payroll. Ask what you are being offered before you accept.

Where Locbase fits

Locbase keeps each session against the workplace it was for, with the rate and your notes, so there is a clear record of who you worked for and on what terms. It does not decide your status or work out your tax.

Questions

Does IR35 apply to locums?

It can, if you work through your own limited company and the booking would be employment if you were engaged directly. It is decided for each booking.

Does IR35 apply if I am a sole trader?

The off-payroll rules are about people working through their own company. As a sole trader the question is whether a booking is self-employment or employment.

What does inside IR35 mean?

That a booking is treated as employment for tax, so tax and National Insurance are taken before payment reaches your company.

Who decides if a booking is inside IR35?

For medium and large clients and public bodies, the client. For small private sector clients, your own company.