Thanks for continuing but I am not sure what you mean by "there should be no problem". Basically I have a dilemma, either i) Declare income (mostly earned in France from UK company) in UK as self-employed sole trader income and pay National Insurance on it but risk having to provide proof that all of work was done in UK. If I cannot prove this and they say "no thanks it's french income so pay it there" then I will have to do either of (ii) and (iii) below. ii) Go back to French authorities and tell them I should have declared this income in France under the small business regime and have to go through penalties and loads of paperwork and accountants fees. iii) Do nothing and take risk that France never asks to see proof that I paid tax on this income in the UK. This is my least favourite option. What would you do ?