NTEP stands for National Type Evaluation Program, which is a non-profit corporation. Scales and other weighing equipment that are NTEP approved have been tested and evaluated to ensure they meet all government standards and requirements. The government standards are set by the NIST (National Institute of Standards and Technology), and are listed in their NIST Handbook 44 The NIST standards cover every aspect of an NTEP approved scale from capacity, accuracy, effects on the scale from temperature and humidity, and even how the manufacturers label is to appear on the scale. It is the standards in the NIST Handbook 44 that your local Weights and Measures inspector(s) will typically use when inspecting your scale and certifying it for use. Each NTEP approved scale will have an NTEP certificate or conformance number listed on it so that your local inspector can obtain a copy of the conformance certificate, and verify that the brand and model of your scale was manufactured within NIST standards.
However, you should always check with your local Weights and Measures Department (or governing agency) as to your scales compliance, as local municipalities can impose rules and regulations that vary both from NIST and NTEP. (NTEP approval does not necessarily mean a scale is “legal for trade” and ready for use “out of the box” in your locale.)