Article VIII, Rule 1.5 of the Supreme Court of Illinois Rules of Professional Conduct
(f) Except as provided in Rule 1.5 (j), a lawyer shall not divide a fee for legal services with another lawyer who is not in the same firm, unless the client consents to employment of the other lawyer by signing a writing which discloses:
(1) that a division of fees will be made;(g) A division of fees shall be made in proportion to the services performed and responsibility assumed by each lawyer, except where the primary service performed by one lawyer is the referral of the client to another lawyer and
(2) the basis upon which the division will be made, including the economic benefits to be received by the other lawyer as a result of that division; and
(3) the responsibility to be assumed by the other lawyer for performance of the legal services in question.
(1) the receiving lawyer discloses that the referring lawyer has received or will receive economic benefit from the referral and the extent and basis of such economic benefit, and
(2) the referring lawyer agrees to assume the same legal responsibility for the performance of the services in question as would a partner of the receiving lawyer.
(h) The total fee of the lawyers shall be reasonable.
Adopted February 8, 1990, Effective August 1, 1990