What a trial balance proves, and what it cannot
A trial balance is a list of every account in your general ledger with its closing balance placed in a debit or a credit column, footed. Because double-entry bookkeeping records each transaction with equal debits and credits, the two column totals must agree. If they do not, at least one posting is wrong in a way arithmetic can see.
That is the whole claim, and it is narrower than most people assume. A trial balance proves that the mechanics of posting held. It says nothing about whether the amounts were right, whether they went to the correct accounts, or whether anything was recorded at all.
It is also not a financial statement. Neither US GAAP nor IFRS requires one and no external reader ever sees it. It exists because it is cheap and it catches the most common bookkeeping failure — a one-sided or mis-keyed posting — before that failure reaches a balance sheet.
Why each account sits in the column it does
Which column an account belongs in is not a convention you memorise — it follows from the accounting equation. Assets sit on the left of Assets = Liabilities + Equity, so asset accounts increase with debits and carry debit balances. Liabilities and equity sit on the right, so they increase with credits.
Revenue and expenses inherit their sides from equity. Revenue increases equity, so revenue accounts carry credit balances; expenses and dividends reduce it, so they carry debit balances. That is why the debit column contains two very different kinds of thing — the assets you own and the costs you incurred. Reconstruct that logic and you never need a mnemonic; the accounting equation calculator works the same relationship from the other direction.
Contra accounts are where most beginners lose the thread. Accumulated depreciation relates to an asset but carries a credit balance because it accumulates the reduction, and so does the allowance for credit losses. Treasury stock and sales returns work the other way. In every case the contra account sits opposite the account it modifies, and putting it on its parent's natural side reliably creates a difference of exactly twice the amount involved.
One more detail decides whether your trial balance foots. In an unadjusted or adjusted trial balance, retained earnings carries the beginning balance, because the closing entries have not run and this period's profit still sits in the revenue and expense accounts. Only in a post-closing trial balance does it show the ending figure, and there the revenue, expense and dividend accounts have gone. Use the retained earnings calculator to prove the roll-forward between the two.
Worked example: a $1,652,800 trial balance that is $900 short
A bookkeeper foots the December ledger of a small contractor and gets these group totals.
- Add the debit column. Assets $709,300 + expenses $918,600 + dividends declared $24,000 = $1,651,900.
- Add the credit column. Liabilities $214,500 + capital and beginning retained earnings $310,000 + revenue $1,032,300 + accumulated depreciation and allowance $96,000 = $1,652,800.
- Take the difference. $1,651,900 − $1,652,800 = −$900. Debits are $900 short.
- Run the nine test. $900 ÷ 9 = $100 exactly. An exact quotient is the fingerprint of transposed digits, because swapping two adjacent digits always changes a number by a multiple of nine.
- Run the halving test. $900 ÷ 2 = $450. If an account with a $450 balance existed, a wrong-column posting would explain it. None does, so the transposition is the better lead.
- Hunt the transposition. The accounts receivable subledger shows a customer invoice of $8,730, and the ledger posting reads $7,830. The 8 and the 7 were swapped. $8,730 − $7,830 = $900.
- Correct and re-foot. Assets become $710,200, the debit column becomes $1,652,800, and both columns now agree.
With the ledger proved, the same figures give the period result: revenue $1,032,300 − expenses $918,600 = $113,700 of net income before adjusting entries. Test the balance sheet side too: net assets of $710,200 − $96,000 = $614,200, against liabilities $214,500 plus opening equity $310,000 plus $113,700 of profit less $24,000 of dividends = $614,200.
How to read the difference: the nine test and the halving test
An out-of-balance difference is not random. Its arithmetic shape tells you which kind of keying error produced it, and checking the shape is far faster than re-reading the ledger.
Divisible by nine. Transpose two adjacent digits and the value changes by nine times their difference, scaled by a power of ten: 54 keyed as 45 changes the amount by 9, and 8,730 keyed as 7,830 changes it by 900. A decimal slide does the same — $540.00 keyed as $54.00 differs by $486, which is 9 × 54. An exact nine quotient tells you to look for a mis-keyed amount, not a mis-posted account.
Even, with a familiar half. Post a debit as a credit and you understate one column and overstate the other by the same figure, so the difference is exactly twice the amount. Half the difference is always a candidate balance to search for, and this is the standard cause when a contra account has been placed on its parent's side.
Equal to an account balance. A whole account omitted shifts the difference by exactly its balance. Count the rows against the chart of accounts before assuming a keying error.
What you must not do is post the difference to a suspense account and carry on. A suspense balance is acceptable only as a temporary marker in a working paper; every month it survives makes the underlying error harder to find.
Normal balance and trial balance column by account type
| Account type | Normal balance | Column | Typical accounts |
|---|---|---|---|
| Asset | Debit | Debit | Cash, accounts receivable, inventory, equipment at cost |
| Contra-asset | Credit | Credit | Accumulated depreciation, allowance for credit losses |
| Liability | Credit | Credit | Accounts payable, accrued wages, unearned revenue, notes payable |
| Contributed capital | Credit | Credit | Common stock, additional paid-in capital |
| Retained earnings | Credit | Credit | Beginning balance in an unadjusted or adjusted trial balance |
| Contra-equity | Debit | Debit | Treasury stock, dividends declared, owner drawings |
| Revenue | Credit | Credit | Sales, service revenue, interest income |
| Contra-revenue | Debit | Debit | Sales returns and allowances, sales discounts |
| Expense | Debit | Debit | Cost of sales, wages, rent, depreciation expense, income tax |
A credit-balance account appearing in the debit column is the single most common cause of a difference that is exactly twice a familiar amount.
What the shape of the difference tells you
| Pattern in the difference | Most likely cause | What to search for |
|---|---|---|
| Divides exactly by 9 — e.g. $900 ÷ 9 = $100 | Two digits transposed, or a decimal slid one place | A posted amount whose digits match a source document in the wrong order |
| Even, and half is a recognisable balance — e.g. $6,400 → $3,200 | One account posted to the wrong column, often a contra account | An account whose balance equals half the difference |
| Equals a single account balance exactly | An account omitted from the trial balance | Missing rows against the chart of accounts |
| Round multiple of 10, 100 or 1,000 | A digit dropped or added while keying | Amounts an order of magnitude away from the source |
| A few cents | Rounding, or a figure entered to the wrong precision | Re-foot both columns at full precision |
| Difference equals the adjusting-entry gap | An adjusting journal entry posted one-sided | The adjustment worksheet, not the ledger |
Multiple simultaneous errors defeat all of these tests. Re-foot after each correction rather than seeking one explanation for the whole gap.
A balanced trial balance is not a correct trial balance
Five error classes pass this test untouched. Omission: a transaction never recorded leaves both columns short by the same amount. Commission: the right amount posted to the wrong account of the same type. Principle: an amount posted to the wrong type of account, such as capitalising a repair. Duplication: the same journal entry posted twice. Compensating errors: two mistakes of equal size on opposite sides. Catching these needs subsidiary ledger agreement, a bank reconciliation, and someone asking of each balance whether it is plausible.
Where the difference usually hides
- A contra account on the wrong side. Accumulated depreciation or the allowance for credit losses placed in the debit column. Produces a difference of exactly twice the balance.
- A one-sided adjusting entry. Depreciation debited with nothing credited. Check that your adjustment worksheet foots on its own before adding it to the ledger.
- Ending retained earnings used in an unadjusted trial balance. Before closing, the account holds the beginning balance; using the ending figure double-counts this period's profit.
- A subledger that disagrees with its control account. Foot the receivables and payables subledgers separately and tie each to the ledger.
- An account listed twice, or a subtotal included with its components. Common when the trial balance is assembled by hand from several schedules.
- A rounding difference from a spreadsheet. Displayed values agree while the underlying figures differ by fractions of a cent. Widen the precision before hunting further.
Where the trial balance sits in the close, and what to run next
A close runs in a fixed order and the trial balance appears twice in it. Post the period's transactions, foot an unadjusted trial balance, then post adjusting entries for depreciation, accruals, deferrals and credit losses. Footing again gives the adjusted trial balance, from which the statements are built. After closing entries transfer revenue, expenses and dividends into retained earnings, a post-closing trial balance confirms that only permanent accounts remain and still agree.
The adjusting entries are where most of the judgement lives, and each has its own arithmetic: depreciation from a depreciation schedule, the credit loss provision from an ageing analysis through the allowance for doubtful accounts calculator. Cash needs its own proof from a bank reconciliation, and inventory needs a physical count.
Once the adjusted trial balance foots, three checks are worth running before you sign off. Prove the balance sheet identity with the accounting equation. Prove the equity movement with the retained earnings roll-forward. And convert the accrual result into cash with the indirect-method operating cash flow calculator, because a profit that produces no cash is the most common sign of an accrual that should not have been recorded. Reading working capital off the same balances gives you a liquidity check at the same time.
Key terms
- Normal balance
- The side — debit or credit — on which an account increases, and therefore the column it occupies on a trial balance.
- Contra account
- An account that reduces the balance of a related account and carries the opposite normal balance, such as accumulated depreciation against equipment.
- Transposition error
- Two digits keyed in the wrong order. Always changes the amount by a multiple of nine, which is why the nine test works.
- Suspense account
- A temporary holding account for an unexplained difference. Acceptable inside a working paper, never in a published statement.
- Post-closing trial balance
- A trial balance drawn after closing entries. Contains only assets, liabilities and equity, with retained earnings at its ending balance.