220 ILCS 30/10.4: Annual gross revenue returns to Commission.

On or before January 30 of each year each electric supplier subject to tax under the provisions of this Act shall file with the Commission an annual gross revenue return for the calendar year ending December 31 of such year and a statement of the amount of tax due for that calendar year on the basis of that return. However, for the tax period July 1, 1981 through December 31, 1981 each electric supplier shall file on or before February 1, 1982 a gross revenue return for the period July 1, 1981 through December 31, 1981 and a statement of the amount of tax due for that period on the basis of that return.

Forms for such returns and amended returns shall be devised and supplied by the Commission.