75 ILCS 5/5-2
If the corporate authorities approve the action of the library board under Section 5-1, they may, by ordinance, or by resolution in the case of a township, provide that the bonds of the city, village, incorporated town or township be issued for the payment of the cost (so estimated as aforesaid) of constructing a building, or remodeling, repairing, improving an existing library building or the erection of an addition thereto, or purchasing a building, site or equipment, or the acquisition of library materials such as books, periodicals, recordings and electronic data storage and retrieval facilities in connection with either the purchase or construction of a new library building or the expansion of an existing library building, or any or all of these things in which event the ordinance or resolution shall also state the time or times when such bonds, and the interest thereon shall become payable. However, the whole of the principal of such bonds and the interest thereon shall be payable within 20 years, and the interest on such bonds shall not exceed the rate permitted in the Bond Authorization Act . The interest may be made payable at such times (annually or semi-annually) as the ordinance or resolution may prescribe. In case the corporate authorities provide for such payment by the issuance of bonds, they shall make provision at or before the issuance thereof, by ordinance or by resolution in the case of a township, which shall be irrepealable, for the levy and collection of a direct annual tax upon all the taxable property within such city, village, incorporated town or township sufficient to meet the principal and interest of the bonds as they mature, which tax shall be in addition to that otherwise authorized to be levied and collected for corporate purposes.
If, however, the corporate authorities do not provide that the bonds of the city, village, incorporated town or township be issued, but otherwise approve the action of the library board, then the library board shall divide the total cost of constructing and financing a building, or remodeling, repairing, improving an existing library building or the erection of an addition thereto, or purchasing and financing a building, site or equipment, or the acquisition of library materials such as books, periodicals, recordings and electronic data storage and retrieval facilities in connection with either the purchase or construction of a new library building or the expansion of an existing library building, or any or all of these things, into as many parts as the trustees determine to spread the collection thereof, and shall certify the amount of one of these parts to the corporate authorities each year during the term over which the trustees have determined to spread the collection. This action by the library board shall be irrepealable. The library board shall specify in its certificate the portion, if any, of the amount to be included in the annual appropriation and library tax levy, and the amount of the special tax required to pay the same as has been approved by the voters.
75 ILCS 5/5-2