Is there any way we can prevent backorders from being allowed on our Cash Account customer profile?
Yes, you can go into File>Customer>Master>General tab and uncheck backorders allowed from the setup>general subtab. You should pair this with a File>Compay>Master setting>Invoice Update cancel B/O based on Customer Flag. This will cancel all backordered items off the order upon invoicing. If you do not change this company setting there will be a note on the order that says customer does not allow backorders but it will not cancel them off the order.