If the business was truly a sole proprietorship, it had no legal existence outside of the owner. However, it is possible that a representative of the owner’s estate has the authority to operate the sole proprietorship after the owner’s death, either from the owner’s will or as authorized by a probate court. 755 ILCS 5/19-6(a). Without the authorization of the estate’s representative, we do not believe that a check written by the authorized signer after the account owner’s death would be properly payable.

The authorized signer’s authority to sign on behalf of the account holder is governed by agency law. Under Illinois law, an agency relationship, like that between an accountholder and an authorized signer, terminates when the principal (the accountholder) dies (unless the agency relationship was irrevocable). Ferguson v. Bill Berger Associates, Inc., 704 N.E.2d 830, 840 (1^st Dist. 1998); Washington v. Caseyville Healthcare Ass’n, 284 Ill. App.3d 97, 101 (5th Dist. 1996). If the signer of a check is not an authorized signer, the check is not properly payable. 810 ILCS 5/4-401(a).