What payment period should I put ?

These notices will only appear on your invoices if the client has not chosen the escrow account ! 

You must always indicate a payment period in the space provided in the quote creation tool. If no period is explicitly agreed upon, French law states that payment must be made within 30 days of the end of the service. 

The invoice is issued at the end of the service. You are free to define a different payment period with your client as long as it does not surpass 60 days from the invoice's issuance date.