What is IR35 and what does it mean for contractors?
  IR35 was first introduced in 2000 by HMRC in an attempt to prevent employees simply working under the same conditions but via a limited company structure. The benefit for the "employee" was a significant reduction in their taxes while the "employer" also saved employers national insurance contributions plus the legal requirements to pay sick, holiday and other statutory employment benefits.

So, IR35 is effectively a set of rules to identify "disguised employees", i.e. those workers who would be classed as employees and thus remove that tax advantages in them setting themselves up this way.

IR35 therefore only really effects contractors, as if you are running a business, employing staff and provide services to several clients then you are very unlikely to be effected by this legislation, however if unsure you should always check first.​
Determining Your Status - Contractor or Employee?
  This is not often black or white and simply reading the terms and conditions of your contract is not sufficient enough. HMRC will look at many aspects when determining your status regarding IR35. This has been a problematic area for both HMRC and the contractor for many years as while some will obviously fall inside or outside of IR35 there are many that fall into a "grey" area depending on how you interpretive the registration and guidance.

From the 1st April 2017, significant changes came into effect within the public sector contractor market in that the IR35 status is now determined by the client and not the contractor. The private sector has not yet been effected although it is assumed it is just a matter of time before it is.

HMRC have released an "Check employment status tool" which can be accessed  here  and is designed to provide you with a determination of your employment status, however we would always recommend getting a professional IR35 review of your contract in addition to using the tool, that way you are mitigating yourself if HMRC were to challenge your employment status, although it would be a tribunal that has the final say.
Contact us so we can help you with you with IR35