You can close the order, which closes all the lines on the order, or you can close the lines separately.
Once an order is closed, it cannot be applied to any more vendor invoices.
The vendor invoice will replace the project cost data once applied.
If you have one order line and plan on making multiple invoices for it, keep in mind that once a single vendor invoice is applied, the order amount will no longer be part of the project cost. One alternative is to make separate order lines in advance so you can pay each line separately and get the order to match up better.
Manually closing an order or line
With the PO open, you can click Close at the top of the order screen, this will effectively close all lines on the order & close the order itself.
If there are multiple lines, you can choose to close individual lines, so you can still process the remaining lines. Keep in mind that once all lines are closed, the order overall is closed as well.
Closing lines when applying to a vendor invoice
When you are adding orders to a vendor invoice, there is a Close checkbox to close the lines as you apply them.
Closing prebilled lines using the accrued order detail report
The accrued order detail report allows you to find accrued prebilled orders and allows you to close them one at a time or by groupings.