A trial balance that doesn't balance is one of the most common — and most avoidable — problems in small business bookkeeping. The good news is that the causes are predictable. Before you start re-checking every voucher from the beginning of the month, work through these five checks in order.
1. Check for one-sided entries
The single most common cause of an imbalanced trial balance is a voucher posted to only one side of the ledger — a debit with no matching credit, or vice versa. This usually happens when a transaction is entered manually and the second leg is forgotten, or when a journal entry is saved before both lines are completed.
If you're working in a spreadsheet, this is easy to miss because nothing stops you from saving an incomplete entry. In a proper double-entry system, every voucher should be validated before posting — debits and credits must match, or the system should refuse to save it.
2. Look for transposed or miskeyed figures
A classic bookkeeping error: entering 4,860 instead of 4,680. The difference between a transposed figure and the correct one is always divisible by 9 — if your imbalance amount divides evenly by 9, a transposition error is very likely the cause. Scan recent entries for numbers that could easily be swapped.
3. Confirm opening balances were carried forward correctly
If your trial balance was fine last month and is off this month, check that opening balances rolled forward correctly at period close. A manual re-entry of opening balances is a common point of failure — even a single account carried forward with the wrong sign will throw off the whole balance.
4. Check for a posting to the wrong account
This won't cause an imbalance on its own — debits and credits can still match — but it will make individual account balances wrong even though the trial balance totals agree. If a specific account looks off rather than the whole trial balance, this is usually the cause. Review recent postings to that account specifically.
5. Check for a duplicated or deleted voucher
If a voucher was entered twice, or entered and then deleted without reversing both sides, the imbalance will usually match the exact amount of that voucher. Search your ledger for the difference amount — if a transaction of that exact value exists, start there.
How a connected ledger prevents most of this
Most of the causes above come from manual re-entry — typing the same figure into a spreadsheet in more than one place, or carrying balances forward by hand. In a general ledger system where every module (sales, purchases, payroll) posts directly to the ledger, these errors mostly disappear, because there's only ever one place a number is entered.