Of all the errors that a trial balance would not reveal, what is the most difficult to detect?

Error of Principal

Error of Omission

Compensating error

Following Errors are difficult to trace in Trial Balance

1) Error of Commission

2) Error of Principle

3) Error of Original Entry

4) Reversal of Entries 

5) Omission of Entries

6) Compensating error

Compensating errors are difficult to detect.