If an incoming payment has been posted and matched to the incorrect customer account in SAP S/4HANA Cloud Public Edition, the appropriate action to correct the mistake is to reset the clearing and reverse the document. This process removes the clearing status of the payment, allowing the payment document to be reversed and corrected. This ensures that the payment is accurately reflected in the correct customer account and maintains the integrity of the financial records.
References:
SAP S/4HANA Cloud Accounts Receivable documentation
SAP Financial Accounting user guides on handling payment errors