Unspent convictions or cautions
When a person is convicted of a crime, that conviction is considered to be irrelevant after a set amount of time. This is known as the rehabilitation period. There are some exceptions in very limited circumstances.
After the rehabilitation period for a conviction has lapsed, the conviction is referred to as 'spent'. This period of time varies according to the sentence received.
A conviction is described as 'unspent' if the rehabilitation period associated with it has not yet lapsed.
Simple cautions become spent immediately at the moment they're issued, while conditional cautions become spent after 3 months.