IEC 61676:2023 specifies the performance requirements of instruments as used in the non-invasive measurement of X-RAY tube voltage up to 150 kV and the relevant compliance tests. This document also describes the method for calibration and gives guidance for estimating the uncertainty in measurements performed under conditions different from those during calibration. Applications for such measurement are found in diagnostic radiology including mammography, computed tomography (CT), dental radiology and radioscopy. This document is not concerned with the safety aspect of such instruments. The requirements for electrical safety applying to them are contained in IEC 61010-1. IEC 61676:2023 cancels and replaces first edition published in 2002, Amendment 1:2008. This edition constitutes a technical revision. It includes an assessment of the combined standard uncertainty for the performance of a hypothetical instrument for the non-invasive measurement of the tube high voltage (in Annex A) which replaces Annex A of the edition 1.1 titled "Recommended performance criteria for the invasive divider".