If you have suffered an injury (physical or psychological) in the last three years as a result of being involved in an accident that wasn’t your fault, then you may have a personal injury compensation claim.
There are some cases where the criteria might be different. For example, a child has three years from their 18th birthday to make a claim (and will be represented in the claim by a competent adult known as a litigation friend), regardless of how old they were when they were injured.