We used TurboTax to file our 2019 taxes. I was just informed that we incorrectly filed a schedule c instead of k-1. How do I amend this? Is TurboTax guaranteed?

WHAT ????

Did you file a Sch C as a sole prop instead of a Partnership 1065 or an S-Corp 1120S ???

Yes we filed a sole proprietor schedule c when in fact it is a multi member LLC and needed a K-1. 

Ok  ... so you are not versed in filing a 1065 so I highly recommend you seek local professional assistance to mitigate the damages you have ... not only does the 1065 need to be filed (and it is very late and the penalties are very costly) but the personal return(s) also  need to be amended.  And no this is not covered by the TT guarantee ... this is a purely a user entry error.