Depending on the status of the transaction's invoicing state (i.e. has it been invoiced, including self billed invoices, or posted, or preinvoiced checked) the original transaction may not be available for editing:
If the transaction has been invoiced, not emailed and not posted, you can delete the invoice to release it for modification
If the transaction has been invoiced and posted or invoiced and emailed, raise a credit note and re-invoice to the correct account.
If the transaction has been pre-invoice checked, you will need to reverse the check before making changes
If the transaction has not been invoiced or posted:
Click Edit on the transaction.
Click the Address tab.
Click in the Switch Address box and select the site address under the new account.
If the site address does not exist, it will need creating.
Click Save.
By moving the transaction to an address under the new account, it will pick up the new account details on save.