Think of it like the incident log a crew fills out right after a crash scene: the first written record that locks in who was hurt, when it happened, and the basic facts before stories start to drift. In legal and insurance use, an employer's first report of injury is the formal notice an employer prepares after a worker is injured or becomes ill on the job. It usually includes the employee's information, the date and place of the incident, how it happened, the body parts affected, and whether time was lost from work. It is a key document in a workers' compensation claim.

Practically, this report starts the paper trail. If it is late, incomplete, or inaccurate, it can slow medical benefits, wage replacement, and the insurer's review of the claim. Details in the report may later be compared against medical records, witness statements, and any dispute over causation or disability. A mistake as basic as the wrong injury date can create a fight that did not need to happen.

In Massachusetts, the employer generally must file an Employer's First Report of Injury with its insurer and the Department of Industrial Accidents under Massachusetts General Laws Chapter 152 when the worker is disabled for five or more full or partial calendar days. The filing deadline is generally within seven calendar days, not counting the day of injury, after the employer learns of it. That can matter in everyday cases too, including injuries tied to rough conditions like spring pothole damage affecting work vehicles.