Can documentation relating to disciplinary warnings be retained after the warnings have expired?

Yes, an employer can keep documentation relating to expired disciplinary warnings provided that it complies with its data protection obligations.

One of the data protection principles is that personal data should not be kept longer than is necessary for the purpose or purposes for which it is being processed. The employer should consider whether or not it is necessary to retain documentation relating to expired warnings. It may be sufficient, and more appropriate, simply to keep a record of the warning instead of all the documentation relating to it. However, if the documentation is relevant, for example to justify a discrepancy in pay levels, it should be retained.