The short answer
A proof of loss is a sworn statement, often on a form the insurer provides, setting out the amount you claim and the basic facts of the loss. Many property policies require one within a set time after the insurer asks for it.
Why it matters
It is usually a condition of payment. In Illinois, it also matters for timing: filing a proof of loss in the form the policy requires pauses the policy’s deadline to sue until the claim is denied in whole or in part.
Where it fits in your case
After a property loss, typically once the insurer requests it. Many policies allow around 60 days after a request, but the deadline depends on the policy.
What to expect
It is sworn. Inaccurate statements can give the insurer a fraud defense, so accuracy matters more than speed.
Estimates are normal. Early figures are often estimates. Say so, and reserve the right to supplement as information develops.
Rejection is not the end. An insurer may reject a proof of loss as incomplete. That usually starts a discussion, not a final denial.
The clock to sue. Many policies require suit within one or two years of the loss. The Illinois pause applies only after a proper proof of loss is filed.
What to do now
Calendar any deadline the insurer sets.
Use the form the policy requires, if it requires one.
Note that amounts are subject to supplementation.
Keep a copy and proof of delivery.
Do not understate the loss to speed up payment.
What we need from you
The policy, the insurer’s request, estimates, an inventory of damaged property, and invoices.
Common misconceptions
“It’s just paperwork.” It is a sworn statement with legal consequences.
“Signing it locks in the amount.” Supplementing is common if it is done properly.
“The deadline to sue waits for the insurer’s decision.” The deadline usually runs from the loss and pauses only after a proper proof of loss.