Before running the statistics report ensure all proformas for arrival up to the period end date have been converted to final invoice.

Then you would setup a report within the Invoicing statistic reports.

There is a helpsheet (no. HS005) which covers this.  Please click on the following link to view or download helpsheet – HS005 Statistics – Deferred Income_Forward Sales.docx or please watch the video below demonstrating this process.