When they are finalized and have been approved by the state of Missouri.
See this TurboTax website for the MO state forms availability - https://care-cdn.prodsupportsite.a.intuit.com/forms-availability/turbotax_mo_online_individual.html
It says they are available to file on turbo tax on l/16/2020 but I still cannot even view them. Could there be a problem? Never had this before. Last year the State made a correction on my return but it did not change any refunds or taxes. It was a turbo tax error which I did call about.
...and you are absolutely sure that none of the other MO tax forms, listed as being ready on ~ 1/30/2020, none of those are included in your tax submission to MO ?
(also, today is the 16th...maybe later, or just before midnight? There have been situations in earlier years, where a late federal change required the "expected" dates to be moved back a week or two). It would be safer if you would wait until well after 1 Feb anyhow.....you may have missed something and amending isn't a task you would want to experience.