(735 ILCS 5/2-616) (from Ch. 110, par. 2-616)
Sec. 2-616. Amendments.
(a) At any time before final judgment amendments may be allowed on just and reasonable terms, introducing any party who ought to have been joined as plaintiff or defendant, dismissing any party, changing the cause of action or defense or adding new causes of action or defenses, and in any matter, either of form or substance, in any process, pleading, bill of particulars or proceedings, which may enable the plaintiff to sustain the claim for which it was intended to be brought or the defendant to make a defense or assert a cross claim.
(b) The cause of action, cross claim or defense set up in any amended pleading shall not be barred by lapse of time under any statute or contract prescribing or limiting the time within which an action may be brought or right asserted, if the time prescribed or limited had not expired when the original pleading was filed, and if it shall appear from the original and amended pleadings that the cause of action asserted, or the defense or cross claim interposed in the amended pleading grew out of the same transaction or occurrence set up in the original pleading, even though the original pleading was defective in that it failed to allege the performance of some act or the existence of some fact or some other matter which is a necessary condition precedent to the right of recovery or defense asserted, if the condition precedent has in fact been performed, and for the purpose of preserving the cause of action, cross claim or defense set up in the amended pleading, and for that purpose only, an amendment to any pleading shall be held to relate back to the date of the filing of the original pleading so amended.
(c) A pleading may be amended at any time, before or after judgment, to conform the pleadings to the proofs, upon terms as to costs and continuance that may be just.
(d) A cause of action against a person not originally named a defendant is not barred by lapse of time under any statute or contract prescribing or limiting the time within which an action may be brought or right asserted, if all the following terms and conditions are met: (1) the time prescribed or limited had not expired when the original action was commenced; (2) the person, within the time that the action might have been brought or the right asserted against him or her plus the time for service permitted under Supreme Court Rule 103(b), received such notice of the commencement of the action that the person will not be prejudiced in maintaining a defense on the merits and knew or should have known that, but for a mistake concerning the identity of the proper party, the action would have been brought against him or her; and (3) it appears from the original and amended pleadings that the cause of action asserted in the amended pleading grew out of the same transaction or occurrence set up in the original pleading, even though the original pleading was defective in that it failed to allege the performance of some act or the existence of some fact or some other matter which is a necessary condition precedent to the right of recovery when the condition precedent has in fact been performed, and even though the person was not named originally as a defendant. For the purpose of preserving the cause of action under those conditions, an amendment adding the person as a defendant relates back to the date of the filing of the original pleading so amended.
(e) A cause of action against a beneficiary of a land trust not originally named a defendant is not barred by lapse of time under any statute or contract prescribing or limiting the time within which an action may be brought or right asserted, if all the following terms and conditions are met: (1) the cause of action arises from the ownership, use or possession of real estate, record title whereto is held by a land trustee; (2) the time prescribed or limited had not expired when the original action was commenced; (3) the land trustee of record is named as a defendant; and (4) the plaintiff proceeds with reasonable diligence subsequent to the commencement of the action to serve process upon the land trustee, to determine the identity of the beneficiary, and to amend the complaint to name the beneficiary as a defendant.
(f) The changes made by this amendatory Act of the 92nd General Assembly apply to all complaints filed on or after the effective date of this amendatory Act, and to complaints filed before the effective date of this amendatory Act if the limitation period has not ended before the effective date.
(Source: P.A. 92-116, eff. 1-1-02.)


(735 ILCS 5/2-617) (from Ch. 110, par. 2-617)
Sec. 2-617. Seeking wrong remedy not fatal. Where relief is sought and the court determines, on motion directed to the pleadings, or on motion for summary judgment or upon trial, that the plaintiff has pleaded or established facts which entitled the plaintiff to relief but that the plaintiff has sought the wrong remedy, the court shall permit the pleadings to be amended, on just and reasonable terms, and the court shall grant the relief to which the plaintiff is entitled on the amended pleadings or upon the evidence. In considering whether a proposed amendment is just and reasonable, the court shall consider the right of the defendant to assert additional defenses, to demand a trial by jury, to plead a counterclaim or third party complaint, and to order the plaintiff to take additional steps which were not required under the pleadings as previously filed.
(Source: P.A. 82-280.)