This filter is applied to use the payment billing address, it is including two parameters.
$address -> is a function used to get the payment billing address.
$ID -> is used to get id.
An example of how you can append additional information: function get_payment_address( $address ) { //it returns payment billing address. return $address; } add_filter( 'rpress_payment_address', 'get_payment_address',10,2 );