Case law is used to determine the IR35 status of a contractor as either
employed (inside IR35) or self-employed (outside IR35).
This article explains what case law is, and provides some guidance for finding
further more detail information about specific cases.
What is Case Law?
Definitions from Duhaime:
If a rule of law cannot be found in written laws, lawyers will often say that
it is a rule to be found in "case law". In other words, the rule is not in the
statute books but can be found as a principle of law established by a judge in
some recorded case.
A basic principle of the law applies whereby, once a decision (a precedent) on
a certain set of facts has been made, the courts will apply that decision in
cases which subsequently come before it embodying the same set of facts. A
precedent is binding and must be followed.
HMRC, IR35 and case law
From the HMRC leaflet IR56:
“The law for tax and social security legislation does not define ‘employment’
and ‘self- employment’. But, over the years, the Courts have considered this
issue and their guidance on whether an individual is an employee or
self-employed is known as case law.”
How should a contractor use case law?
A contractor would not be wise to try and learn all the IR35 case law, and
employment law, with a view to ‘doing it on their own’.
Firstly, this would be a huge task costing a great deal of time and is best
left in the hands of professional lawyers.
Secondly, as a novice ‘lawyer’, trying to combat status disputes with HMRC significantly reduces your chance of success.
However, what is useful is for a contractor to have a good overview of the
process of mitigating the IR35 risk, and knowing when to get professional help.
The following articles are recommended reading:
Case law applicable to IR35
This section is more applicable for those wishing to dive into the detail of
the case law.
They have published the case law section of their employment status manual on
ESM7000 – Case Law
Bear in mind that not all these cases are directly applicable to IR35.
Overview of background case law, including:
Express & Echo Publications v Tanton 
Carmichael v National Power Plc 
Smith & Chanton Group v Costain Ltd 
Chen Yuen v Royal Hong Kong Golf Club 
McManus v Griffiths 
Hall (Inspector of Taxes) v Lorimer 
McMenamin v Diggles 
O'Kelly v Trusthouse Forte Plc. 
Swan Hellenic Ltd v Secretary of State 
Massey v Crown Life Insurance Co. 
Ready Mixed Concrete Ltd v. Minister of Pensions & NI 
Market Investigations Ltd v Minister of Social Security 
Detail for IR35 Cases, including:
Synaptek v Young (2003)
LIME IT v Justin (2002)
FS Consulting v McCaul (2001)
Battersby v Campbell (2001)