Every ISO/IEC 17025 accredited lab needs to be diligent about uncertainties, including all testing labs. In fact, all ISO/IEC 17025 accreditation visits must include verification that the laboratory has demonstrated this diligence. There must be a documented procedure in the system describing how uncertainties are handled. For some testing labs, this may be a simple statement that all tests are qualitative and not quantitative and they do not need to determine any uncertainties. Most testing labs do not need to calculate or demonstrate what we call ISO-GUM uncertainties for all relevant uncertainties for tests on their scope of accreditation. They rarely if ever might report an uncertainty on any test report either. They only need to demonstrate to their ISO/IEC 17025 assessors with a few specific examples how they would calculate those MUs for a customer requesting them.