Title 43, Chapter 14, Section 9
(a) Every person holding a license issued by a division of the board
shall display it in a conspicuous manner at his place of business.
(b) All commercial vehicles used by licensees and certificate
holders exclusively in the daily operation of their business shall
have prominently displayed thereon the company or business
registration number issued by the Secretary of State's office. Such
registration number shall also be prominently displayed on any
advertising in telephone yellow pages and newspapers relating to
work which a licensee or certificate holder purports to have the
capacity to perform. Said registration number shall also be printed
on all invoices and proposal forms.