Printing your checks on regular paper is technically possible, but it's not recommended for several reasons. To prevent fraud, different security measures, such as microprinting and watermarks, are included on standard check stock paper. Regular paper lacks these features, making your checks more liable to fraud.
If you do not have a recent notice issued to you by IDOR from which you can obtain a Letter ID, then you can select the link “Request a Letter ID” under the 'Individuals' panel on the MyTax Illinois homepage. You must have previously filed a tax return with IDOR in order to activate a logon.