In Odoo 17, the purchase order number stores in the "name" field. To import your own PO numbers, make sure your Excel file includes the PO numbers under the "name" column.

If this still doesn’t work, check if there’s any custom code or module that overrides the PO numbering sequence.

Ensure you have a column name (or Order Reference) in your import file.

This simplified import structure will in fact have you import your Purchase Orders with a 'custom' PO number:

Hi,

In Odoo 17, purchase order numbers are always generated by the system’s sequence, so they change automatically when you import POs. If you want to keep your supplier’s PO reference, you should use the Vendor Reference field (partner_ref) instead of trying to override the PO number. Overwriting the name field is technically possible but not recommended, as it can break Odoo’s numbering consistency.

Hope it helps