Typical documents that may be needed are:
1) Social Security documents - this is to ensure all spellings and numbers will be correct on your tax return
2) Drivers License or State ID
3) IL-PIN if one has been issued to you by the state of Illinois and/or IP PIN if one has been issued
4) Prior year tax returns (up to 3 years depending on type of return)
5) Income documentation (W-2, 1099s, Schedule K-1, etc)
6) Tax deduction documentation (1098, 1098-T, etc)
7) Business documentation
8) Other documentation as needed for support