Ideally, an accident report should be completed at the time of the incident noting what happened, who witnessed both the accident and the conditions that caused the fall along with any other relevant information such as lighting. The requirement for a report is generally a store or business policy, rather than mandated by law.
If a report is not completed at the business location or occurred at private location or was not observed by others, compile a record of what happened yourself. Include information such as:
A description of the circumstances
Who was present
The comments made by those who saw or helped after the fall
If possible, take photos of the area. If you were physically hurt, have your injury checked out immediately to help substantiate your claim.