It’s possible to be both employed and self employed at the same time. This could be the case if you are working for a company part-time but also taking on freelance work simultaneously. If this is the case, you would be liable to pay tax and National Insurance on income in two different ways.
If you are an employee you will receive a payslip every time you are paid. Your payslip will clearly show your gross pay, Income Tax and Class 1 National Insurance contributions. These deductions are paid via your PAYE tax code and determine your net pay.
If you are registered Self Employed you are must submit a Self Assessment tax return before the January 31st deadline. You will pay any Income Tax and National Insurance contributions via this service. Both your tax and National Insurance are calculated during Self Assessment and the amounts you pay are based on the income / profit that you declare.
Self Employed and Employed at the same time?
When completing a Self Assessment tax return, you must include your employment earnings and declare any tax that has already been paid via PAYE accordingly.