Illinois Statutes Chapter 750. Families § 5/402. Legal Separation

(a) Any person living separate and apart from his or her spouse may have a remedy for reasonable support and maintenance while they so live apart.

(b) Such action shall be brought in the circuit court of the county in which the petitioner or respondent resides or in which the parties last resided together as husband and wife. Commencement of the action, temporary relief and trials shall be the same as in actions for dissolution of marriage, except that temporary relief in an action for legal separation shall be limited to the relief set forth in subdivision (a)(1) and items (ii), (iii), and (iv) of subdivision (a)(2) of Section 501. If the court deems it appropriate to enter a judgment for legal separation, the court shall consider the applicable factors in Section 504 in awarding maintenance. If the court deems it appropriate to enter a judgment for legal separation, the court may approve a property settlement agreement that the parties have requested the court to incorporate into the judgment, subject to the following provisions:

(c) A proceeding or judgment for legal separation shall not bar either party from instituting an action for dissolution of marriage, and if the party so moving has met the requirements of Section 401, a judgment for dissolution shall be granted. Absent an agreement set forth in a separation agreement that provides for non-modifiable permanent maintenance, if a party to a judgment for legal separation files an action for dissolution of marriage, the issues of temporary and permanent maintenance shall be decided de novo.