Q585: How long do I have to report an incident to the police?

It depends upon the type of incident you are reporting. This area of law is very complex so the following is a basic guide only (as there are exceptions).

Road Traffic Accidents

Reportable road traffic accidents (see questions in related information for more details) have to be reported as soon as is reasonably practicable and in any case, within twenty-four hours. Some forces may not take a report of a road traffic accident after a specified amount of time.
Minor road traffic incidents (e.g. failing to wear a seatbelt) have a time limit on prosecution so, therefore, must be reported within 6 months (e.g. failing to wear a seatbelt)
Serious road traffic incidents (e.g. dangerous driving) have no such time limit for prosecution.

Crime

Most crimes do not have a time limit for reporting them.
The crimes that do have time limits are 'summary only' which means that they can only be tried at a Magistrates Court and are relatively minor offences; they must be prosecuted within 6 months (e.g. common assault, harassment and take without owners consent (TWOC)).

Do bear in mind that the longer the period between the incident happening and reporting the matter to the police the harder it will be for the police to gather the evidence.