So many questions as to why this is something you’d want to do. Also there could be so many things related to “stop all invoicing”
1. You could update all roles for all users so there is only view permissions for Invoice, Cash Sales, Deposits and Payments transactions
2. If you have scripts making invoices you could use the scripted records page for Invoices and cash sales to undeploy all scripts
3. Disable billing schedules
4. Review all integrations for ones creating invoices
5. Create a workflow with 2 return user error action on before record load and before record submit for all contexts and event type saying “A/R transactions are not permitted
6. Use manage accounting periods to lock AR for the period or all periods