What Is IR35? A Plain-English Guide to Off-Payroll Working Rules
A plain-English explanation of IR35, who it affects, when it applies, and what the status decision is really asking.
IR35 is the common name for tax rules aimed at off-payroll working. It applies when a worker provides services through an intermediary, such as a personal service company, and the arrangement would look like employment if the worker were engaged directly.
Who This Is For
Businesses engaging independent professionals through personal service companies or similar intermediaries.
Finance, procurement, and legal teams responsible for off-payroll governance.
Workers and suppliers who need to understand how a status determination affects payment handling.
When This Applies
When services are supplied through an intermediary rather than by direct employment.
When the real working practices may point towards employment if the contract were direct.
When a private-sector client is not within the small-company exemption, or when public-sector rules apply.
Detailed Explanation
IR35 is not a separate employment law status. It is a tax framework used to decide whether a worker operating through an intermediary should, for tax purposes, be treated more like an employee in that engagement.
The core test is practical rather than cosmetic. HMRC expects the decision-maker to look at the real agreement between the parties and the actual working practices, not just the contract heading or a preferred label.
That is why IR35 projects often go wrong when they rely on template paperwork alone. If substitution rights, control, supervision, mutual obligations, and day-to-day realities do not match the written contract, the paperwork is not enough.
The operational burden sits with different parties depending on the structure. In many cases the client has to decide status, and the fee-payer may have to operate PAYE and National Insurance if the engagement is inside the rules.
For commercial teams, the practical takeaway is simple: IR35 is a workflow issue as much as a legal one. The business needs a consistent process to identify off-payroll engagements early, gather evidence, communicate determinations, and connect those outcomes to the way the worker is actually paid.
Frequently Asked Questions
Is IR35 only relevant to IT contractors?
No. The rules are sector-neutral. They can apply anywhere a worker supplies services through an intermediary and the engagement may resemble employment.
Does the contract alone decide IR35 status?
No. HMRC guidance says the real agreement and working practices matter. Written terms are only part of the picture.
What does 'inside IR35' usually mean operationally?
It usually means the engagement is treated more like employment for tax purposes, and the fee-payer may need to apply PAYE and National Insurance obligations.
What tool does HMRC provide?
HMRC provides Check Employment Status for Tax, usually called CEST. HMRC says it will stand by the result where the information entered is accurate and not contrived.
Official Sources
This guide is general information, not tax or legal advice. Check the current HMRC and GOV.UK guidance before relying on it for a live engagement.