If it comes to light when matching an invoice to a purchase order that the PO has incorrect distributions, you should make the changes at the invoice processing stage (rather than returning to the PO and correcting the error there).

If you feel the PO distributions require altering then:

• Within AP match the PO to the invoice as normal (with the incorrect distributions).
• Enter two new lines: the first a negative line to remove the value from the incorrect distribution and the second a positive line to the correct distribution code.
• Be careful to remove the PO number that defaulted in on both your new lines as you do not want to unmatch the PO.

This will leave the PO status as 'Matched' and the GL entries as required  - more detailed guidance is available [1].  

The system tolerance levels, used when comparing the purchase order line amounts and invoice amounts, have been changed in the Accounts Payable module to allow invoices with a 5% variance (up to a maximum of £100) to proceed without creating a hold.