Basic tax considerations if you come to work in the UK
If you come to live in the UK there are basic tax considerations that you will need to observe. Most importantly, you will be required to pay tax on your income (in excess of any allowances) if you come to live in the UK. Income includes; wages, benefits, your pension and savings interest. If you’re employed your employer will deduct Income Tax from your wages. Otherwise, you will likely be required to prepare and submit a Self-Assessment tax return if you work for yourself or you have other UK income.
You will also usually be required to pay National Insurance if you work in the UK. How much you pay will depend on whether you are employed or self-employed. There are countries with whom the UK has bilateral agreements and where you may not be required to pay National Insurance for the first 52 weeks you are in the UK; as long as you meet the necessary conditions.
You will not have to pay UK tax if you only make short business trips here, for example, a training course or meeting. There is a special process that can be used if you have overpaid tax in the UK and are a foreign national.
Source: HM Revenue & Customs | 27-11-2019