This report, developed under the MetCCUS project, provides a comprehensive good practice guide for fiscal metering in Carbon Capture, Utilisation, and Storage (CCUS) systems. Accurate and traceable CO₂ flow measurement is essential for regulatory compliance, emissions accounting, and commercial transactions across the CCUS value chain. The document addresses the selection, implementation, and calibration of fiscal metering systems, focusing on both technical and regulatory aspects. It evaluates key metering technologies—Coriolis, ultrasonic, differential pressure, and turbine meters—highlighting their performance under various CO₂ conditions. The guide also explores the influence of thermophysical properties, fluid composition, and phase behaviour on measurement accuracy. The report integrates lessons learned from recent research and standardisation efforts, offering actionable insights for stakeholders involved in the deployment of fiscal metering systems in CCUS projects.