Hi, Is there a way to stop system emails being sent to the suppliers when a PO is being closed or information updated on it?

Make sure that the "TO BE E-MAILED" checkbox is not checked on your PO under the Communication subtab.

the box is not ticked on the PO but is ticked on the Supplier as we want the email to be sent when the PO is approved, but not on updates

Do you have any customization around it? Because as far as I know, there is no TO BE E-MAILED checkbox on the supplier/vendor.

no customisation

This is a standard preference to attach the transaction.