Does the state of Wisconsin tax pension income from an Illinois corporation and if so, at what rate?

Yes, if you are a Wisconsin resident receiving a pension from Illinois. If you didn't live in Illinois in 2017, then you won't pay tax in Illinois, only Wisconsin.

Here's information from the Wisconsin Department of Revenue about the Retirement Income Exclusion:

A taxpayer (and/or his or her spouse if MFJ) may subtract up to $5,000 of certain retirement income if both of the following are true.

 • The taxpayer (or spouse if MFJ) was 65 year of age or older on December 31, 2017, and

 • The taxpayer’s federal AGI is less than $15,000 ($30,000 if MFJ). If MFS, the sum of both spouses’ federal AGI must be less than $30,000. 

The remainder of the retirement income is taxed at the regular state rate, which is 4% on the first $14,790 of taxable income. 5.84% on taxable income between $14,791 and $29,580. 6.27% on taxable income between $29,581 and $325,700.7.65% on taxable income of $325,701 and above.