I did e-file Iowa state for the additional fee.
Somewhere it said to fill and sign IA 8453-IND within one day of acceptance.
Then what? So I had the same question, but found the correct answer here, in the form instrutions, apparently not available from State of Iowa.gov
Ref https://www.esmarttax.com/tax-forms/iowa-form-ia-8453-ind-instructions/
See this line: (notes and bold added)
Return the completed form ( IA 8453-IND ) to the ERO ( Electronic Return Originator)
or paid preparer, unless self-prepared. If self-prepared, retain the IA 8453-IND.
