The 10-year rule is most often used to refer to a legal loophole in UK planning regulation.  If the land has been developed unlawfully, the best course of action is to submit a retrospective application – if this course is not followed, an enforcement notice may be issued listing drastic alterations that must be made to the property by law. Alternatively, if no enforcement is taken within four years of development completion, it is granted immunity from enforcement action. This loophole also exists in a 10-year form when dealing with a change of use in the property.

These loopholes are extremely risky ways of avoiding planning regulation – Norton Taylor Nunn strongly advises against the use of such methods.