810 ILCS 5/9-104

(a) Requirements for control. A secured party has control of a deposit account if: (1) the secured party is the bank with which the deposit account is maintained; (2) the debtor, secured party, and bank have agreed in a signed record that the bank will comply with instructions originated by the secured party directing disposition of the funds in the deposit account without further consent by the debtor; (3) the secured party becomes the bank's customer with respect to the deposit account; or (4) another person, other than the debtor: (A) has control of the deposit account and acknowledges that it has control on behalf of the secured party; or (B) obtains control of the deposit account after having acknowledged that it will obtain control of the deposit account on behalf of the secured party. (b) Debtor's right to direct disposition. A secured party that has satisfied subsection (a) has control, even if the debtor retains the right to direct the disposition of funds from the deposit account.