Equitable access to timely genomic testing for people affected by rare diseases is required to provide an accurate diagnosis early enough to inform key clinical decisions that modify outcome. This Position Statement describes best practice guidance for the specialist genomics workforce within the national health services in the UK and Ireland. It includes recommendations relating to workforce, data infrastructure, training for service users, standardised laboratory practice to maximise diagnostic yield, service development informed by patient experience, innovation through research to continually improve service quality, and capacity management. Our overarching objective is to facilitate high quality diagnostic genomic testing delivered efficiently and effectively within a clinically relevant timeframe. (By Professors Sian Ellard, Emma Baple and Robert Taylor, https://jmg.bmj.com/content/early/2024/09/26/jmg-2024-110228 )