Errors that are NOT revealed by the Trial Balance

The trial balance is a list of all the general ledger balances. Each ledger account part of the general ledger will have either a debit or credit balance. Since the general ledger entries are all double entries, it follows that the resulting balances should also balance.

The trial balance is essentially a control system that helps identify and evaluate errors made. There are however limitations. The following are the types of errors that are not revealed by the trial balance:

1. Error of Omission: no entry at all in a case when there should have been
2. Error of Commission: entry to the wrong individual account. 
3. Error of Principle: entry to the wrong type of account e.g. $100 posted to assets instead of purchases. (both are debit entries)
4. Error of Original Entry: wrong amounts are posted to both credit and debit
5. Error of Reversal: correct amounts are posted to the correct accounts but on the wrong sides
6. Error of Transposition: posting $123 instead of $321 on both sides
7. Compensating errors: two or more erros that compensate each other

The trial balance can still be a useful accounting control system however. The following mistakes are revealed:

1. Posting to one side only
2. Posting both entries to one side only
3. Posting different figures to each side
4. An individual account added up incorrectly
5. Opening balance not brought down
6. Balance in the trial balance is different from balance on the account (extraction error)