You need to add additional income to your Schedule C as Uncommon Income which covers interest.
To do this in TurboTax Online you can follow these steps:
- Within your tax return use the magnifying glass icon to search Schedule C
- Use the Jump to link that appears in the results
- Click Edit for the Schedule C you want to add the income to
- Scroll down and click Add Income for this work
- Mark the Uncommon income, includes awards, interest, debt previously deducted line and enter the amount from your 1099-INT