from citizen's advice:
If you have to stop, you must remain near the vehicle long enough for anyone who is involved directly or indirectly in the accident to ask for details. This could be, for example, the owner of an injured animal, a relative of someone who is injured, or the police. The driver must then give their name and address, the name and address of the owner of the vehicle (if the driver is not the owner), and the registration number of the vehicle.
The driver may also have to report the accident to a police officer or at a police station, in person, as soon as practicable and in any case within 24 hours. This duty arises whenever the driver has not given their name and address at the scene of the accident, whether or not they were asked to do so.
Failure to report can lead to:
Each offence can result in an instant driving ban, but in normal circumstances, you should expect a means tested fine up to £2,500 and between 5 and 10 penalty points. In extremely serious cases, punishment can include community service, a curfew order or a prison sentence.