I am assuming you are referring to a Standard Purchase Order. If this is the case, the PO total amount is not stored on the base table PO_HEADERS_ALL, hence you cannot find it on the archive table as well.
The PO Header total amount is the sum of all lines amount. You cannot track the total amount at header level, because it simply does not exist. What you can track is the amount changes at line level.
I hope it helps.
Do you know the table where the amount changes at line level are tracked? Is it stamped with a revision number? I can then use that to sum up those lines at a certain revision number to get the PO Header at a certain point of time.
assuming you are archiving, the 4 main po tables also have corresponding archive tables
Headers: po_headers_all - po_headers_archive_all
Lines: po_lines_all - po_lines_archive_all
Shipments: po_line_locations_all - po_line_locations_archive_all (summing price_override * quantity for all your uncanceled shipments here would get you total amount, based on your revision_num)
Distributions: po_distributions_all - po_distributions_archive_all
Releases (if you use): po_releases_all - po_releases_archive_all
Each of the archive tables have REVISION_NUM as a column so you can link using that and the po_header_id to gather data for each revision.
I think for the header table the LATEST_EXTERNAL_FLAG = 'Y' is the most recent change.
another thing to keep in mind - creation date of the header might be different from creation date of the lines/shipments so be sure to ask your user which date they want to drive the report.
Thank you for all of your information, especially the last point about checking the creation date of the header vs the lines. Do you think it possible to sort the query (to support the report) by Revision Date?
I do see Revised_date on the PO Header