+#modeled after owed
+sub payable {
+ my( $self, $field ) = @_;
+ my $balance = $self->$field();
+ $balance -= $_->amount foreach ( $self->cust_credit_bill_pkg($field) );
+ $balance = sprintf( '%.2f', $balance );
+ $balance =~ s/^\-0\.00$/0.00/; #yay ieee fp
+ $balance;
+}
+