Before going for preperation of financial statements we 
have to get tallied the trial balance. The trial balance 
proves the arthematical accuracy of the books of accounts.
Even though it is tallied therer are some possibilities of 
errors which canot be detected by trial balance they are 
1.Errors of principle
2.Compensating errors
3.Errors of commission
4.errors of ommission

Errors are of two types
1. Error of principal
2. Clerical Error
   a. Compensating errors
   b. Errors of commission
   c. Errors of om mission