OBJECTIVES: To i) demonstrate compliance with the Commissioning for Quality and Innovation for venous thromboembolism risk assessment ii) to undertake root cause analysis of Hospital Acquired Thrombosis and to investigate its impact on quality of care. DESIGN: Prospective monitoring of all admissions. SETTING: Imperial College Healthcare Hospitals, London. PARTICIPANTS: All Hospital Provider Spells as defined on the NHS Data Model and Dictionary. MAIN OUTCOME MEASURES: i) Percentage of patients undergoing Venous Thromboembolism Risk Assessment (VTE-RA) at and 24-hours after admission ii) root cause analysis of Hospital Acquired Thrombosis up to 90 days following discharge. RESULTS: Over a 48-month cycle 83% were overall VTE-RA assessed with 36% in the first 12 months but with significant improvement to ≥95% between April 2013 and April 2015, achieving compliance target since April 2012 involving a massive 633, 850 Spells over the 4 year period. We undertook root cause analysis of all VTE episodes from April 2013 to March 2014, to ascertain Hospital Acquired Thrombosis (HAT), we analysed 433, 174 inpatient days and found a HAT rate of 1 per 1000 with 23% and 24% for DVTs and PEs potentially avoidable respectively. We further analysed VTE risk stratification (n = 1000) and found 37.0% at high risk, 44.4% at medium risk and 18.6 % at low risk, indicating the need of thromboprophylaxis in 81.4% (high and medium) of whom 33.6% were excluded. CONCLUSIONS: We achieved 95% RA compliance which has favourably impacted on our daily practice and improved the quality of the clinical care.