A trial balance difference is a clue, not an instruction to invent a balancing entry. A one-sided posting creates a difference equal to the missing side. Moving a decimal point creates a slide error. Reversing two digits creates a transposition whose difference is divisible by nine. These tests narrow the search; none identifies a transaction by itself.
Some errors leave the columns equal. Omitting both sides, recording an entry twice, or using the wrong expense account still produces balanced books. Compare the ledger to source documents as well as checking arithmetic. Correct the cause and preserve a short explanation so another bookkeeper can follow the repair. Never use an unexplained suspense amount to conceal a difference.