Changes can be made to transaction reconciling details as long as this is done on the same business day the transaction was marked as reconciled and saved.
We recommend making corrections to distribution errors right away. Once it has been posted overnight, a journal entry will be needed to make the correction. Denying a PCard statement only allows adding documentation, not modifying a Project ID or account codes to posted transactions.
The PCard Manual for reconcilers lists step-by-step instructions for How to Unreconcile a PCard Transaction.