You will find Angel Investment Credit within the Illinois tax return at the screen Take a look at Illinois credits and taxes under Business and Investment Credits.
The printable form Illinois Schedule 1299-C Angel Investment Credit may be found here.
See this TurboTax Help.
Thanks for replying but it's not one of the available choices in my screen.
Here is a suggestion from DMarkM1, and RobertB4444 that has worked for other customers in your situation.
DMarkM1 says "In your online version enter a fictitious business that you will delete later. Just enter some simple basic information and then only some minor income and no expenses. Once done go back into the IL interview to see if the business section is now visible. Make all your entries there for your credit. Then go back and delete the business from your federal interview."