During the configuration of the Requester matrix you can decide for some fields whether they are to be mandatory or optional.
The procedure is the same whether you're connected to Xero, QuickBooks Online or NetSuite; here, we're showing it for Xero.
This is how you make certain fields mandatory
In the main menu, find your Organisation and go to Approval workflows under Workflows and settings.
Open the respective workflow and, in the Creation step, click on the Matrix icon.
Select the fields you want to be mandatory and click on DONE.
Please note: Depending on the workflow, some fields are always mandatory.