Invoices often have purchase orders or billing codes that the recipient needs to record when processing the invoice. We have just added support for this in ParaPlan Billing.
When generating a new invoice, enter the billing code or PO into the Reference field and we will display that value on the invoice. We will also remember this Reference and associated it with the funding source. This means the next time an invoice is generated for that funding source, the Reference field will be pre-populated.