in short Illinois allows a deduction for these dividends by filing form 1299-C each year if included in federal taxable income
abbott letter
https://www.abbottinvestor.com/static-files/3899893c-6874-4824-89ae-7e137419618b
abbvie
Https://investors.abbvie.com/static-files/35fb1849-bc14-44fe-9a3b-740bb1dc81a8 \
for your information generally these letters are posted on the company's website under shareholder/investor relations
two other publicly traded companies in a HIB zone are Caterpillar and Walgreens
you may even be able to file online
https://tax.illinois.gov/programs/mytax/il-1040-x.html
if you extended your Illinois 2020 return you have until about 10/15/2024 to file an amended return to claim a refund.prior years - it's too late
you are correct. the 1040/1299-C Illinois instructions contain no details about companies whose dividends qualify for a subtraction being either a River Edge Redevelopment Zone or High Impact Business within a Foreign Trade Zone.
as to river edge qualified companies even less info is available
see this website
https://dceo.illinois.gov/
