Indiana Code Title 25. Professions and Occupations § 25-28.5-1-35

Sec. 35. (a) A plumbing contractor licensee shall prominently display the licensee's license in the licensee's principal business office.  In the case of a partnership or corporation, the license of at least one (1) partner, member, or officer of the corporation, or the corporate license, must be displayed.

(b) The license number of a licensed plumbing contractor must be recognizably displayed in all forms of written or printed advertising for plumbing services and on all vehicles that are used to provide plumbing services.

(c) A plumbing contractor, partnership, or corporation must maintain a register listing:

The register must be available for public inspection upon request.

(d) A plumbing contractor, journeyman plumber, or apprentice plumber shall carry a facsimile of that person's license or certificate of registration on a job location where the person is engaged in plumbing contracting or the trade of plumbing.  The plumbing contractor, journeyman plumber, or apprentice plumber shall display that person's license or certificate of registration upon the demand of a state inspector or local building or plumbing inspector in Indiana within that inspector's local jurisdiction or upon a customer's request.