Can you use one PO for multiple invoices?

Yes — one PO can be billed across multiple invoices, and it happens constantly: partial shipments (supplier delivers 60 units now, 40 next month, invoicing each delivery), staged services billed by milestone, and 'blanket POs' that authorize a quantity or budget to be drawn down over months of smaller deliveries.

The bookkeeping rule that keeps this sane: every invoice references the same PO number, and each one is matched against the quantities actually received to date, with the PO tracking the running balance (ordered vs received vs invoiced). The PO stays open until fully delivered and billed, then closes.

Where it goes wrong is spreadsheet-land: nobody tracks the drawdown, the supplier bills 110% of the original quantity across five invoices, and no single invoice looks wrong. Line-level receiving against the PO is the fix.