510 ILCS 40/8

Except as otherwise provided in this Act, it shall be unlawful to use any brand for identifying any livestock, unless such brand has been recorded as provided in this Act. When a recorded brand is applied to livestock which have been branded by a previous owner, such brand shall be applied so as not to overlap, disfigure, or mutilate the existing brand or brands.

Brands consisting of letters only, arabic numerals only, or a combination of both, may be used for "in-herd" identification; provided, they are located at least 10 inches away from any recorded brand. Such "in-herd" brands are not to be recorded and shall not be considered evidence of ownership.