You cannot sign a form to avoid paying tax unless you are a student working in your holidays. You can earn around �91 (freepay)a week before you pay tax, and if you have a P45 from the Job Centre (if you have been claiming Job Seekers Allowance) your new employer will take into account the unused �91s from 6 April to the date you start work. If you do not have a P45 it will take the Revenue a few weeks to issue you with a proper code, which will then allocate the unused freepay to date, and you will get a refund. If you leave, and will not be working or claiming JSA again before the end of the tax year, you will be entitled to have the balance of your freepay for the year set against your earnings. You will need to contact the Tax Office;they will send you a form to sign, which you submit with your P45. National Insurance works quite differently, and you will not be due any refund of contributions.