NOTE FOR HURRICANES HARVEY AND IRMA POLICYHOLDERS: The initial Proof of Loss requirement is being waived. When the adjuster visits and assesses your flood damage, he/she will work with you to document your claim, and submit a report for consideration to the insurance company. The payment amount will be determined after the insurer reviews the report. However, you will need a Proof of Loss (deadline to submit is one year from the date of the flood loss) if you find additional flood damage; if you disagree with what the insurance company pays you; or if your contractor's estimate is more than the estimate on the initial report sent to the insurance company.
The below information discusses how the NFIP ordinarily uses POLs. The below is NOT the process being used for Hurricanes Harvey and Irma.
Your adjuster may assist you in preparing a Proof of Loss (which is your sworn statement of the amount you are claiming including necessary supporting documentation) for your official claim for damage. A Proof of Loss can be many things, but must contain the specific details set forth in the Standard Flood Insurance Policy. You'll need to file your Proof of Loss with your insurance company within 60 days of the date of loss.
You'll receive your claim payment after you and the insurer agree on the amount of damage and the insurer has your complete, and signed Proof of Loss. If major catastrophic flooding occurs, it may take longer to process claims.
Note: Signing a Proof of Loss does not waive your rights to file for additional claim payments in the future if additional damage is discovered.
Note: The requirement to file the Proof of Loss could be waived by FEMA depending on the severity of the event. Your adjuster or insurance company will let you know if this happens.
Information is from https://www.fema.gov/nfip-file-your-claim