How do I change my filing status on turbotaxonline from single to head of. Household?

This won't be an option until you have already entered a qualifying dependent. 

Then, you can change your filing status. 

Here's how to do this in TurboTax Online:

1. While logged into your TurboTax account, navigate to the left of the screen, under 2024 Taxes, choose My Info

2. At the top of the screen, under Your Info appears your name, click your name to expand options, then choose Edit

3. Continue through the interview pages until you arrive at About your household

4. Answer the question "What was your marital status on December 31, 2024? to change your filing status

Here is some more information on filing status: How to Change Your Tax Filing Status