Errors a trial balance cannot find
Objective: Identify error types that do not disturb trial-balance equality.
Recommended first: Preparing a trial balance
| Error | Balances? | Why |
|---|---|---|
| Omission | Yes | Nothing posted on either side |
| Commission (wrong account, same type) | Yes | Equal amounts posted |
| Principle (wrong class) | Yes | Equal amounts posted |
| Complete reversal | Yes | Both sides swapped equally |
| Original entry (wrong amount both sides) | Yes | Both sides use the wrong figure |
| Duplication | Yes | Both sides doubled |
| Compensating errors | Yes | Two errors cancel |
Because many errors leave totals equal, bookkeepers rely on other checks: reconciling bank and card accounts, agreeing subledgers to control accounts, comparing this month with last month, and reviewing source documents for anything recorded twice or not at all. In the error detective simulator, you diagnose which kind of error occurred and whether the trial balance would catch it.
Check your work
- Would this error change total debits or total credits?
- Which outside evidence would reveal it?
- What correcting entry fixes it?
Rent of $500 was debited to Equipment. Debits and credits still equal $500, but assets are overstated and expenses understated.
| Account | Debit | Credit |
|---|---|---|
| Equipment (wrong) | $500.00 | |
| Cash | $500.00 |
Common mistakes
✗ Assuming the books are right because totals match.
✓ Review source documents and unusual balances.
Guided practice
Use hints freely here.
Item 1 of 2
Error detective: error of omission?
A $900.00 supplier bill for repairs was never entered in the books. Identify the type of error, whether the trial balance will still balance, and the difference between total debits and total credits (enter 0 if it balances).
Independent practice
Try these without hints. Completing the lesson needs at least one independent item solved without revealing the answer.
Item 1 of 10
Error detective: error of principle?
A $500.00 payment for this month's rent was debited to Equipment; Cash was credited correctly. Identify the type of error, whether the trial balance will still balance, and the difference between total debits and total credits (enter 0 if it balances).
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Key terms
- Error of principle
- Posting to the wrong class of account.
References and provenance
- OpenStax, Principles of Accounting, Volume 1: Financial Accounting (accessed 2026-10-29)
Original lesson written for Bookkeeping Exercises (AI-assisted drafting). Calculations are verified by the platform's automated accounting tests. Not yet reviewed by a credentialed accountant. Updated 2026-10-29.