As with any claim, the insurer needs to know two things:

Firstly, to check that cancellation cover has been contractually acquired (i.e. to know the reason for cancellation and that this reason is justified),
Secondly, to determine the amount of the claim, i.e. the amount still to be paid by you.

You will be asked to provide

The purchase invoice for your trip
The cancellation invoice issued by the service providers
The cancellation scale (which you can find in the general terms and conditions of sale)
Proof of the reason for cancellation (death certificate, medical certificate, social security statement, certificate of cancellation of holiday, etc.).

What is a cancellation fee? 

When you cancel your holiday, you are liable for all or part of the price of the services cancelled, known as the cancellation fee. 

These costs are calculated according to a scale indicated in the general terms and conditions of sale for your trip.

Please note: The insurer is entitled to ask you for any additional proof that would enable it to understand and justify the reason for cancellation.