Customers want their purchase order number on tax invoice, but there is no field for po number included when raising a job. Would like this to be added and linked to P.O Number field on invoices
This could be that it's not added to your invoice template as this functionality does exist.
See in the example below this invoice (based on the sales order tax invoice template) has the customers PO and also the internal SO number on the invoice.
To add during the raising of a job, the process in Reckon Accounts is to create a sales order.