Did you import your W-2, and also key it in yourself?

You might accidently entered the form twice. Review your entries and delete an extra form, if needed. 

Here's the general procedure for deleting unwanted forms, schedules, and worksheets in TurboTax Online:

1. Open your return in TurboTax.
2. In the upper right corner, click My Account > Tools.
3. In the pop-up window, select Delete a form.
4. Click Delete next to the form/schedule/worksheet and follow the onscreen instructions.