A balanced trial balance only shows that debits equal credits. Some errors leave the totals equal, so your accounts can be wrong while the check says they are fine.
This page helps if you have finished a full exercise and the marked answer shows a different profit or asset. The background is in explaining errors that do not disturb agreement.
What kinds of error hide from the trial balance?
Think of a shopkeeper who counts the money in and out of the drawer and finds the two match. She could still have put a sale in the wrong notebook. The count does not tell her that.
The same happens in accounts. The four usual kinds are listed in classifying accounting errors: omission, commission, principle and reversal.
Worked set: four errors, one balanced trial balance
This is an original set for a fictional business. Each transaction below was recorded wrongly, yet the trial balance still balances.
| Transaction | What was done | The error |
|---|---|---|
| Invoice from supplier, RM800 | Not recorded anywhere | Omission |
| Rent paid, RM500 | Debited to electricity instead of rent | Commission |
| New equipment bought, RM2 400 | Debited to purchases | Principle |
| Cash received from a customer, RM300 | Debit receivables, credit cash | Reversal |
Each fault still distorts the final statements. The unrecorded invoice understates both purchases and payables. The rent in the wrong account leaves total expenses right but puts the amount under the wrong heading.
The equipment posting is the largest: gross profit is understated by RM2 400, because an asset was treated as a trading expense. The reversed receipt has each side swapped, so the totals still match while receivables and cash are both wrong by RM600.
A checking routine that works
Try these four steps in order, on paper, after any full exercise.
- Compare the answer with what you expected. Which line looks odd?
- Trace that line back to its ledger account, then to the source document.
- Ask of each entry: is this an asset, an expense or something else? Is it in the right account?
- Check the direction. Did money come in or go out, and does the debit match?
This routine can find a method error in a few minutes. Rereading all the figures takes much longer.
What to do with the mistake
Write it in a log with its type, for example “principle, equipment posted as purchases”. The mistake log and paper-error review gives a format. After two weeks, look for the type that repeats.
Then practise that type with writing correcting journal entries, which shows how to fix each kind without disturbing other accounts.
When one-to-one tuition may help
If the same type of error returns after you have logged it, a teacher can watch your working live and see the decision point where it goes wrong. The lesson covers why each entry is needed, not only how to balance the totals.
See online one-to-one Accounting tuition for how to start, or read the trial balance chapter first to rebuild the foundations yourself.