225 ILCS 330/15
Every professional land surveyor shall have a reproducible seal , which may be computer generated, the impression of which shall contain the name of the land surveyor, his or her place of business, the license number of the professional land surveyor , and the words "Professional Land Surveyor, State of Illinois". A professional land surveyor shall seal all documents prepared by or under the direct supervision and control of the professional land surveyor . Any seal authorized or approved by the Department under the Illinois Land Surveyors Act shall serve the same purpose as the seal provided for by this Act. The licensee's written signature and date of signing along with the date of license expiration shall be placed adjacent to the seal. The licensee may provide, at his or her sole discretion, an original signature in the licensee's handwriting, a scanned copy of the document bearing an original signature, or a signature generated by a computer.
It is unlawful to affix one's seal to documents if it masks the true identity of the person who actually exercised direction, control, and supervision of the preparation of that work. A professional land surveyor who seals and signs documents is not responsible for damage caused by subsequent changes to or uses of those documents where the subsequent changes or uses, including changes or uses made by State or local governmental agencies, are not authorized or approved by the professional land surveyor who originally sealed and signed the documents.
225 ILCS 330/15