You can modify invoices in the Draft status in case their PO# or date has changes, or you need to add or remove some work orders.
Tap a draft invoice, and then tap Edit.
Tap PO# field, and enter a new purchase order number.
Tap the Date field, and then in the date picker, tap the appropriate date and tap Save.
Tap a work order (anywhere except the Remove icon) to modify it.
Tap Add or Remove to attach or detach work orders.
Tip Learn how to attach and detach work orders in draft invoices.