This Technical Bulletin (No. 0045) from the National Security Inspectorate provides guidance on the implementation of BS 102000:2018, the updated British Standard for the provision of investigative services, which supersedes the 2013 version. The document outlines mandatory compliance requirements for NSI-approved companies, detailing significant changes such as enhanced definitions, revised vetting processes, and the introduction of the inference cycle in investigations. Companies seeking or maintaining NSI approval must adhere to these updated standards and will be audited accordingly. Manual review recommended for complete details.