10 ILCS 5/20-2.2
Any non-resident civilian citizen, otherwise qualified to vote, may make application to the election authority having jurisdiction over his precinct of former residence for a vote by mail ballot containing the Federal offices only not less than 10 days before a Federal election. Such application may be made on the official postcard or by facsimile or electronic transmission. A request pursuant to this Section shall entitle the applicant to a vote by mail ballot for every election in one calendar year at which Federal offices are filled. The original application for ballot shall be kept in the office of the election authority for one year as authorization to send a ballot to the voter for each election to be held within that calendar year at which Federal offices are filled. A certified copy of such application for ballot shall be sent each election with the vote by mail ballot to the election authority's central ballot counting location to be used in lieu of the original application for ballot. No registration shall be required in order to vote pursuant to this Section. Ballots under this Section shall be delivered by the election authority in the manner prescribed by Section 20-5 of this Article in person, by mail, or, if requested by the applicant and the election authority has the capability, by facsimile transmission or by electronic transmission. Ballots voted under this Section must be returned postmarked no later than election day and received for counting at the central ballot counting location of the election authority during the period for counting provisional ballots, the last day of which is the 14th day following election day.
10 ILCS 5/20-2.2