Disagreement between your Balance Sheet and your Accounts Payable Aging report could be the result of future payments made against current bills.
The Accounts Payable Aging report (like other Accounts Payable Detail reports), does not include bills with a status of Paid, so, while they may seem to disagree, both the Balance Sheet and the Accounts Payable Aging Detail reports are correct because the bill is no longer open.
If necessary, you can generate a Vendor Balance report that agrees with the Balance Sheet. To do so, customize the Vendor Balance report to run as of the date on the Balance Sheet and change its Aging method to Report Date.
Alternatively, you can customize the Accounts Payable Aging report to the As of Report Date. The report will then agree with the Balance Sheet as long as the Balance Sheet follows the accrual reporting method for the same date range.
For more information: Follow these steps to match mismatched Aging Reports in QuickBooks Online.