Amended state returns cannot be e-filed in TurboTax unless it's for state of New York or Vermont only; and they have to be current tax year in order to e-file those. All other amended returns (including prior year amends) have to be mailed when using TurboTax software.
For Michigan, you'd need to use the e-filing system on that state's website in order to e-file an amended return; if they state that they allow e-filing of them.
Per Michigan Department of Treasury: "When should I file an amended Michigan return?
File a Michigan amended return only after your original return or claim has been filed and processed. If you are claiming a refund on your amended return, you must file it within four years of the due date of the original return (including approved extensions). For example, to amend a 2013 return that was not extended, Form MI-1040X-12 must be postmarked by April 15, 2018.
If a change on your federal return affects your Adjusted Gross Income (AGI) and/or your exemptions, you must file an amended Michigan return within 120 days of the change. Include a copy of your amended federal return with all applicable schedules and supporting documents. Submit payment of any tax and interest due."
Can I e-file an amended state return?
https://ttlc.intuit.com/replies/6032704
