In the sales and purchasing modules, the tunnel to access customers and suppliers is always available even if the invoice is posted.
In addition, it is enabled in all sales and purchasing documents (orders, deliveries, returns, invoices...), but in the A/P-A/R module you cannot use the tunnel to view and access the customer or supplier record if the invoice is posted.
This control is not understood in A/P-A/R invoicing when it doesn't exist in sales and purchases.