Do businesses file W-2's and transmittal forms to Illinois?

No, as of September 28, 2009

Only for businesses of 250 or more employees, which must register and file electronically in a special format.

Smaller businesses do NOT have to submit W2s, but must keep paper copies in case the government ever asks for them.

See Title 86, Part 100, Section 100.7300.

Also, IL did away with quarterly 941 filings in 2012. Businesses still pay through MyTaxNet, but do not have to file quarterly reports.