退税以前我记得是雇主帮你搞定的(不知道记错没有)

补充:刚才查了一下
a P45 is issued to an employee when they leave a period of employment. The document provides details of all tax and other deductions made during the current tax year. A 4-Part form, the first part is sent to HMRC by the employer, the remaining parts are retained by the departing employee. When the employee starts a new job, they should hand the new employer parts 2 and 3 of the P45, and retain part 1A for their own records.