Can I Still Convert a Sales Order to an Invoice Without Creating a Requisition First?

Yes, you can. If a sales order has no requisitions linked to it, it will be converted to an invoice directly as usual with no additional restrictions.

Requisitions only become mandatory in the following cases:

• If you enabled the “Generate Requisition” checkbox when creating the sales order.
• If you created a requisition for the sales order using the “Create Requisition” button on the view page.

In other words, what governs the ability to convert is not the activation of the feature itself, but whether or not requisitions are linked to the sales order. If no requisition has been created, the conversion proceeds normally.