Use the worksheet below to calculate the portion of Illinois Business income or losses that needs to be included on your Illinois return. If there is more than one business, you will calculate each business separately and then add the subtotals to enter the full amount attributable to Illinois on your return.
Total Sales Inside Illinois
Total Sales Everywhere
Illinois Income Apportionment Formula (IAF)
IAF decimal (figured above)
Amount of business income or loss from Federal return, Form 1040, Line 12
Illinois Apportioned Income
PART YEAR RESIDENTS (calculate the Illinois Apportioned Income above and continue below):
Illinois business income or loss incurred during your period of residency
Illinois Apportioned Income (from above)
Total Illinois business income or loss. Enter this amount on your return.