For the GL Trial Balance to be in balance:
the Last Year Closing column must total to zero.
the Debit and Credit columns for Period To Date (PTD) must have the same total for the period.
the Debit and Credit columns for Year To Date (YTD) must have the same total for the year.
If any of the above are not true, then your GL Trial balance is out of balance.
To find where this has occurred so that you can take steps to fix it do the following:
Check the Last Year Closing column:
If the Last Year Closing column does not total to zero, this needs to be fixed first to get a correct starting point, by importing opening balances. See: Import opening balances after entering last year adjustments.
Once the import has completed, re-run your Trial Balance for your current period to see if this has rectified the imbalance. If not move to the next step.
Screen the GL Trial Balance YTD for each period:
Go to General Ledger, Reports. Financial, Trial Balance.
Set Display PTD/YTD Balances as Display YTD Only.
Print the report for your last period, note any imbalance in the Debit and Credit totals.
Print the report for each prior period until you find which period the imbalance occurred in, for example: if the Trial Balance balances for period 4 but not period 5 or 6, and the difference in periods 5 and 6 are the same, then the error occurred in period 5.
Print the General Ledger Batch Report for the period
Go to General Ledger, Reports, Transactions, General Ledger Batch Report.
In Period select the period in which the imbalance occurred as determined at Step 2.
Set Print Summary Only to Yes.
Click Submit and find which Batch is incorrect, the out of balance batch will be marked by an Out of Balance warning message.
Note down what type of batch it is e.g.: Journal, Customers, etc.
Go to the batch and edit it so as to add the missing transaction lines. For example, for a Customers batch, go to General Ledger, Transactions, Other Modules, Journals from Other Modules, select the Batch No and Accept (F9) to enter the batch, then List (F4) to view all transaction lines in the batch. You need to review the transactions and work out what line/s are missing. You can just add a line for the difference and post it to a Suspense account until you have time to work it out.
Check for individual GL accounts that are not balanced
Periodic Inventory: If you are running Periodic Inventory, see: Periodic Inventory. Check if opening and closing entries have been entered correctly (equal each other for closing and subsequent opening journals) as per the details in the article.
Partial Update: Run Tools, Company, Utilities, Recalculate GL Balances in Report Only mode. Any results found indicate a partial update. Archive immediately and run the utility in Update Account Balances mode. For more details, see: Recalculate GL Balances and GL Batch Headers utilities.