I'm trying to populate a header field on the Check and Deposit transactions created from the Match Bank Data page (Add Charge and Add Deposit). Unfortunately, it's not working at all. I tried all possible triggers. Entry, Before Record Load, Before Record/User Submit, After Record Submit.

Try with schedule workflow

But the field is mandatory which is why I would like to populate it before save

You should make the field mandatory using a separate workflow that only targets standard contexts like User Interface, Web Services, CSV Import, etc. Since the creation from the Match Bank Data page doesn’t use a standard UI context, those workflows won’t trigger — that’s expected behavior. So the solution is: • Use one workflow to enforce the mandatory field only for standard contexts. • Then use a Scheduled Workflow (or a Scheduled Script) to populate the field after the transaction is created by the Match Bank Data process. This way, you avoid blocking NetSuite’s internal creation logic, and still ensure the field is populated correctly across all cases.

Thank you. Although that would mean I have to script or create a workflow for all other transaction types to make it mandatory. It's meant to be mandatory across all transaction types.