10 ILCS 5/5-23
Any registered voter who changes his residence from one address, number or place to another within the same county wherein this article 5 is in effect, may have his registration transferred to his new address by making and signing an application for such change of residence upon a form to be provided by the county clerk. Such application must be made to the office of the county clerk. In case the person is unable to sign his name the county clerk shall require such person to execute the request in the presence of the county clerk or of his properly authorized representative, by his mark, and if satisfied of the identity of the person, the county clerk shall make the transfer.
Upon receipt of such application, the county clerk, or one of his employees deputized to take registrations shall cause the signature of the voter and the data appearing upon the application to be compared with the signature and data on the registration record, and if it appears that the applicant is the same person as the party previously registered under that name the transfer shall be made.
Transfer of registration under the provisions of this section may not be made within the period when the county clerk's office is closed to registration prior to an election at which such voter would be entitled to vote.
Any registered voter who changes his or her name by marriage or otherwise, shall be required to register anew and authorize the cancellation of the previous registration; provided, however, that if the change of name takes place within a period during which such new registration cannot be made, next preceding any election or primary, the elector may, if otherwise qualified, vote upon making the following affidavit before the judges of election:
I do solemnly swear that I am the same person now registered in the .... precinct of the .... ward of the city of .... or .... District Town of .... under the name of .... and that I still reside in said precinct or district.
(Signed) ....
If the voter whose name has changed still resides in the same precinct, the voter may vote after making the affidavit at the polling place regardless of when the change of name occurred. In that event, the affidavit shall not state that the voter is required to register; the affidavit shall be treated by the election authority as authorization to cancel the registration under the former name, and the election authority shall register the voter under his or her current name.
Suitable forms for this purpose shall be provided by the county clerk. The form in all cases shall be similar to the form furnished by the county clerk for county and state elections.
The precinct election officials shall report to the county clerk the names and addresses of all such persons who have changed their addresses and voted. The city, village, town and incorporated town clerks shall within five days after every election report to the county clerk the names and addresses of the persons reported to them as having voted by affidavit as in this section provided.
The county clerk may obtain information from utility companies, city, village, town and incorporated town records, the post office or from other sources regarding the removal of registered voters and notify such voters that a transfer of registration may be made in the manner provided by this section.
If any person be registered by error in a precinct other than that in which he resides the county clerk shall be empowered to transfer his registration to the proper precinct.
Where a revision or rearrangement of precincts is made by the board of county commissioners, the county clerk shall immediately transfer to the proper precinct the registration of any voter affected by such revision or rearrangement of the precincts; make the proper notations on the registration cards of a voter affected by the revision of registration and shall notify the registrant of such change.
10 ILCS 5/5-23