When an employee is issued with a formal warning, should the employee be required to sign and return a copy of the warning letter?

As a matter of good practice, it is advisable for an employer to ask an employee to sign and return a copy of any letter recording a formal disciplinary warning, so there is a record that he or she has received it. However, there is no requirement for the employee either to acknowledge or to "accept" the warning for it to be valid. It is sufficient for the employer to give the employee a copy of the warning and retain a copy on his or her file.