The P45 is an official tax document in the United Kingdom. It is given by an employer to an employee when the employee leaves his job. If the P45 form is lost, it is not possible to get a replacement.
A P45 is a four-part document. Part 1 is sent to the Inland Revenue. Part 1a is for the employee's records. Parts 2 and 3 are intended for the new employer. A P45 contains information about an employee's tax code. It summarizes total income and tax paid so far that tax year. If an employee does not have a P45 when he starts a new job, he may initially pay too much in taxes.