The auto-calibration feature of a balance may not be relied upon to the exclusion of an external performance check. For a scale with a built-in auto-calibrator, we recommend that external performance checks be performed on a periodic basis, but less frequently as compared to a scale without this feature. The frequency of performance checks depends on the frequency of use of the scale and the criticality and tolerance of the process or analytical step. Note that all batches of a product manufactured between two successive verifications would be affected should the check of the auto-calibrator reveal a problem. Additionally, the calibration of an auto-calibrator should be periodically verified—a common frequency is once a year—using National Institute of Standards and Technology (NIST)-traceable standards or NIST-accredited standards in use in other countries.