N.Y.C. Admin. Code § 20-461: § 20-461 Display of license.

a. Each general vendor shall carry his or her license on his or her person and it shall be exhibited upon demand to any police officer, authorized officer or employee of the department or other city agency.

b. The general vendor's license shall contain his or her name, his or her license number and a non-removable photograph of the licensee. It shall be worn conspicuously by him or her at all times while he or she is operating as a general vendor.