The article linked below gives you a general idea of what many states expect you to do regarding using certified legal for trade class III scales when it comes to selling produce at a farmers market or produce stand. Generally, in most states anyone selling fruits and vegetables by weight to customers must use a state inspected legal for trade certified scale which has a certificate of conformance number. Complying with the rules takes two steps. First, the seller needs to purchase a NTEP approved legal for trade scale (our site can help you with that). Then the legal for trade scale must be inspected and approved by your individual state. See more info below.
Scales must conform to National Type Evaluation Program (NTEP) standards. Scales that comply with NTEP guidelines typically will be marked with the NTEP logo and the associated accuracy class which is normally “III” with produce scales. Scales marked “not legal for trade” are not acceptable for retail use in Tennessee. Scales must also comply with the National Institute of Standards and Technology (NIST) Handbook 44 (H44) which mandates tolerances, specifications and other technical requirements for all weighing and measuring devices. Both NTEP and H44 requirements are national standards utilized by the vast majority of all states. See article