The Medical Certificate of Stillbirth (MCS) records data about a baby's death after 24 weeks of gestation but before birth. Major errors that could alter interpretation of the MCS were widespread in two UK-based regional studies. A multicentre evaluation was conducted, examining MCS issued 1 January 2018 to 31 December 2018 in 76 UK obstetric units. A systematic case-note review of stillbirths was conducted by Obstetric and Gynaecology trainees, generating individual 'ideal MCSs' and comparing these to the actual MCS issued. Anonymized central data analysis described rates and types of error, agreement and factors associated with major errors. There were 1120 MCSs suitable for assessment, with 126 additional submitted data sets unsuitable for accuracy analysis (total 1246 cases). Gestational age demonstrated 'substantial' agreement K = 0.73 (95% CI 0.70-0.76). Primary cause of death (COD) showed 'fair' agreement K = 0.26 (95% CI 0.24-0.29). Major errors 696/1120; 62.1% (95% CI 59.3-64.9%) included certificates issued for fetal demise at <24 weeks' gestation 23/696; 3.3% (95% CI 2.2-4.9%) or neonatal death 2/696; 0.3% (95% CI 0.1-1.1%) or incorrect primary COD 667/696; 95.8% (95% CI 94.1-97.1%). Of 540/1246 43.3% (95% CI 40.6-46.1%) 'unexplained' stillbirths, only 119/540 22.0% (95% CI 18.8-25.7%) remained unexplained; the majority were redesignated as either fetal growth restriction FGR: 195/540; 36.1% (95% CI 32.2-40.3%) or placental insufficiency 184/540; 34.1% (95% CI 30.2-38.2). Overall, FGR 306/1246; 24.6% (95% CI 22.3-27.0%) was the leading primary COD after review, yet only 53/306 17.3% (95% CI 13.5-22.1%) FGR cases were originally attributed correctly. This study demonstrates widespread major errors in MCS completion across the UK. MCS should only be completed following structured case-note review, with particular attention on the fetal growth trajectory.