Verify that there is a sales tax item in the items list for the correct sales tax percentage rate.
Verify sales tax settings on the invoice window. There are three fields that impact sales tax.
On each line item in the body of the invoice window, the last column should show a 'T' indicating that item is taxable. At the bottom of the invoice screen the field indicating the customer is 'Taxable'. The field just to the left of the totals should show the sales tax rate i.e. 6.5% or the rate for your area.
Sales tax is paid to state, not IRS, therefore QuickBooks does not have a sales tax form for IRS, nor does it have the form for state sales tax. The states usually have a fill in form on their website, that you may use the sales tax liability report info to complete the state reporting.
Hope this is helpful.