Two employers, one in UK and one abroad

Hello, I am a British citizen, employed by a UK-based company. Over the last year, I have been a non-executive board member for a company based in Luxembourg. I have a contract with them for 1 day/month and I receive an income. How should I pay taxes? Am I self-employed for this second job? Many thanks, 

Name removed admin .

Hi L T,
You are an employee of an overseas company and receive foreign employment income.
If you travel to Luxembourg to carry out the work you are employed to do, then you can be taxed by the Luxembourg tax authorities, as well as the UK.
If you are still in the UK or another country besides Luxembourg, you are taxable in the UK.
In either case, you would declared this income on a a paper SA102 (employment) and if foreign tax is deducted on SA106 (foreign).
You should use the equivalent sections of an online tax return.
Thank you.