DEATH OR MAJOR INJURY
If there is an accident connected with work and:
* Your employee, or a self employed person working on your premises is killed or suffers a major injury or:
* A member of the public is killed or taken to hospital
YOU MUST INFORM THE ENFORCING AUTHORITY WITHOUT DELAY.
WITHIN 10 DAYS YOU MUST FOLLOW UP WITH A COMPLETED ACCIDENT REPORT FORM
For more informnation see the link below.
OVER THREE DAY INJURY
If there is an accident connected with work and your employee, or a self employed person working on your premises, suffers an over three day injury you must send a completed accident report to the Incident Contact Centre or your enforcement authority.
An over three day injury is one which is not major but results in the injured person being away from work or unable to do the full range of their normal duties for more than three days not counting the day of the injury itself.
For more information on RIDDOR see this
link