Start by separating SaaS billing flows
Map each recurring revenue flow before choosing software: French VAT-liable B2B customers, French consumers, EU business customers, non-EU customers, trials converted to paid plans, annual prepayments, usage-based charges, refunds and credit notes. French official guidance separates e-invoicing for transactions between French VAT-liable businesses from transaction e-reporting for consumers or foreign operators, so one generic subscription invoice rule is not enough.