If you don't have any assets that are being depreciated as part of your business, you can simply "downgrade" your product using the "Clear and Start Over" feature. Just keep in mind that any data you've entered will be deleted. See the TurboTax FAQ below for instructions.
"Can I downgrade to a lower-priced version of TurboTax Online?"
https://ttlc.intuit.com/replies/3288495
You can also delete a Schedule C that has automatically transferred into your 2018 return by using the instructions below. Be sure to read the FAQ carefully, as you may need to officially "dispose" of the business you no longer have.
https://ttlc.intuit.com/replies/3300011
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
