You only need to report 1 Schedule C on your federal return. Do not create a separate schedule C unless you have a completely different business (ex: if you also did dog grooming business, you would need to Schedule Cs). Your federal Schedule C will be for your income and expenses related to the popcorn sales.
You will file a non-resident return for AZ and part-year resident returns for CA and SC. Florida does not have an income tax, so no need to file a Florida return. When you do the state returns, you will allocate the income and expenses from your 1 federally-filed Schedule C to each state. In order to get TurboTax to generate the appropriate state tax returns, you will enter these states in the My Info section (left side menu).
Sign into your return, click on Take me to my return or click on Personal Info at the top if you are using desktop software. You will indicate that you lived in SC and CA and enter the dates and then scroll down and add AZ to the ''Other state income'' section, see image attached. It is a little different in the desktop software where you will enter your resident state and then list all other states you need a return for in the ''Other state Income'' area.
In the example image below, I have listed FL as my resident state, so I added all the other states to the ''Other State Income'' list. TurboTax will start a state return for each state in this list and you can add as many as you need. And then when you do the state return, you adjust the business income to reflect only the amount attributable to that state.
The 3rd screenshot is for LIVING in multiple states. TurboTax will generate resident state returns for these states, but you allocate the business income in the same manner as you do for the nonresident states.
