I'm here to share some information about how the Sales Tax Liability report works
The amount in your Sales Tax Liability report is based on the sales receipt and invoices you've created. If you have nontaxable deposits, then the report won't match. You may follow these steps in determine which deposits are taxable:
Go to the Reports menu.
Under Sales and customer, choose Deposit Detail.
Click the Customize button, then set the appropriate reporting date.
Under Rows/Columns, add the Taxable option.
Click Run report.
I've also included some articles that will help you in managing your sales tax in QBO: