charlie

it is normal to work under 20 hrs a week.  

Your annual income is below 5525 will have no tax deduction, the numbers in different years may vary.

Sometimes if you have not set up your tax code right, it may deduct your payment,  or you are doing different jobs at the same time it will also affect.

The tax can be refunded each year.  Please refer to other post in the forum for tax refund.