You follow the instructions on the notice from the Ohio Dept. of Taxation (ODT).
The most common notice is for failure to file a School District Income Tax (SDIT) return (SD-100).
To verify or find out if you live in a school district with an income tax enter your address at:
http://www.tax.ohio.gov/Individual/LocalTaxInformation.aspx
TurboTax (TT) does not automatically prepare a School District return, you must initiate it.
At the screen, in the Ohio program, titled "A few things before we wrap up your state taxes"
scroll down to School District taxes.
Or later at the screen "Your 2020 Ohio Taxes are ready for us to check"
-Click Other situations
-Scroll down to School District taxes.
At this point, you may actually find it easier to do an SDIT return by hand, than in TT. For the form, see https://www.tax.ohio.gov/portals/0/forms/ohio_individual/individual/2020/SDIT_SD100_Bundle.pdf