The Happy Accountant

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The financial consequences of being inside IR35 are mainly (there are other consequences) you lose the tax-avoidance facility of dividends. 
Essentially, if you are within IR35, you must calculate a “deemed payment” and pay NICs and PAYE (tax) on that deemed payment.
The tax-deductible amounts that you can claim in travel and expenses will also be affected.

HMRC publishes an introduction and a list of guiding questions to help you to decide whether you fall inside or outside IR35.
You will need to examine whether IR35 applies on a “contract by contract” basis.  It is possible to have some contracts within IR35 and some outside IR35
The circumstances of your “intermediary” is also a [...]

Although, traditionally IR35 affected IT contractors and engineers, the legislation is not actually limited to a particular trade, occupation or business sector.
If you personally perform services for your customer, through an intermediary, but you could be deemed an employee of your customer if it were not for the existence of the intermediary, you could fall [...]

IR35 was first propsed in 1999 and was introduced into UK legislation in 2000. The primary aim has been to prevent the avoidance of tax and national insurance by trading through an intermediary (commonly a limited company) rather than being an employee.
Prior to IR35, individuals could form a limited company and invoice their “client”/”employer” and [...]