When you take out a pet insurance policy, you provide information to the insurer, about your pet, your circumstances, any health history and so on. The insurer uses that information to decide whether to offer cover and at what price. The statement of fact is their record of what you told them.
It usually arrives with your policy documents when your cover starts, and again at renewal. It lists things like your pet's name, breed, age, whether they're neutered, any pre-existing conditions you declared and the cover level you've chosen.
The reason it matters is that your policy is based on this information being accurate. If something on the statement of fact is wrong, whether because you made an error when applying, the insurer recorded something incorrectly or your circumstances have changed, that inaccuracy could affect a claim further down the line.
The insurer's position if a claim comes in that's affected by inaccurate information on the statement of fact is that the policy was based on incorrect details, which can complicate or in some cases invalidate the claim. It's not a comfortable situation to be in when you're already dealing with a sick or injured pet.
So the simple habit is: when your statement of fact arrives, check it. Make sure your pet's details are right, that any declared conditions are recorded correctly and that nothing is missing. If anything is wrong, contact your insurer and get it corrected straight away in writing.
"If something on the statement of fact is wrong, that inaccuracy could affect a claim further down the line."