On Form 1040, Line 2A
On TurboTax: Federal Taxes-> Wages and Income -> 1099 Int-> Box 8
It's reported on line 2a of Form 1040.
To enter tax exempt interest -- whether it's on a Form 1099-INT or not -- in TurboTax Online:
If you receive a Form 1099-INT, you'll need to include the amount shown in Box 1 on the “taxable interest” line of your tax return. Report any tax-exempt interest shown in Box 8 of the 1099-INT on the “tax-exempt interest” line of your tax return. The total would be entered on line 2a of your Form 1040.
You can enter Tax Exempt Interest by following these steps in TurboTax: