You are able to downgrade to a lower version if you have not already paid for the version you are in, but you will have to use the Clear & Start Over feature to do that. See steps below for how to Clear & Start Over https://ttlc.intuit.com/replies/4248526
NOTE: Keep in mind that each version handles different situations, so if you downgrade and your tax situation calls for more than what that version handles, you will get prompt to upgrade again.
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