Since there wasn't much entry needed for the simplified method, the easiest way would be to delete a home office form from your return and reënter.

To delete the form in TurboTax Online:

1. Sign in to TurboTax, if you're not already signed in, and open your return. Make sure you've gone past the blue simple and accurate screen.
2. In the upper right corner, click My Account > Tools.
3. In the pop-up window, select Delete a form.
4. Select Delete next to Schedule C -- Form 8829 (or if you are claiming the home office deduction as an employee it will be Form 2106 -- Form 2106 Adjustments Wks -- Employee Home Office Wks) 

To enter your home office expense along with other common business expenses (See the attached screenshot below. Click to enlarge.):

·         Type “Schedule C” in the Search box.

·         Select the “Jump to” link.

·         Select Add expenses for this work (or Edit and navigate down to Business Expenses).