OK...
If you have an Advantage subscription where you receive the software each year in November then see this TurboTax support FAQ for canceling the subscription - https://ttlc.intuit.com/community/downgrading/help/how-do-i-cancel-my-turbotax-advantage-subscriptio...
Other than the Advantage subscription, just do not start a tax return using TurboTax or purchase any TurboTax products
