Are you working as a contractor? You may be liable to pay tax under IR35 regulations.
The rules for IR35 are extremely complex, but in essence you will be liable for IR35 payment if you are a contractor who does not meet HMRC's definition of 'self-employed'.
If you receive remuneration from an employer through an intermediate arrangement (such as through a company you own) you may be avoiding certain tax liabilities - in which case HMRC will deem you liable for IR35. HMRC will consider you to be a 'disguised employee' - using the system to take advantage of tax breaks you may not be entitled to.
Whether you should pay IR35 tax or not will depend upon your individual situation, the type of contract you are working on and various working practices.
If you are a contractor, but you are not self-employed, in the view of HMRC they may consider you to be subject to the same rate of tax and National Insurance obligations as an employee.
To help you maximise your earnings as a contractor, speak to the Sky Accounting team for personalised advice.