BACKGROUND: Routine monitoring of outcomes for patients with Acute Kidney Injury (AKI) is important to drive ongoing quality improvement in patient care. In this study, we describe development of a case-mix adjusted 30-day mortality indicator for patients with post-hospitalisation AKI (H-AKI) across England, to facilitate identification of any unwarranted centre-variation in outcomes. METHODS: We utilised a routinely collected national dataset of biochemically detected AKI cases, linked with national hospitals administrative and mortality data. 250,504 H-AKI episodes were studied in total, across 103 NHS hospital trusts, between January 2017 - December 2018. Standardised mortality ratios (SMRs) were calculated for each trust using logistic regression; adjusting for age, sex, primary diagnosis, comorbidity score, AKI severity, month of AKI, and admission method. RESULTS: Mean 30-day mortality rate was high at 28.6%. SMRs for 23/103 trusts were classed as outliers, 12 above and 11 below the 95% control limits. Patients with H-AKI had mortality rates over 5 times higher than the overall hospitalised population in 90/136 diagnosis groups and over 10 times higher in 60/136 groups. Presentation at trusts with a co-located specialist nephrology service was associated with a lower mortality risk, as was South Asian or Black ethnicity. Deprivation, however, was associated with higher mortality. CONCLUSIONS: This is the largest multi-centre analysis of mortality for patients with biochemically ascertained H-AKI to date, demonstrating once again the considerable risk associated with developing even mild elevations in serum creatinine. Mortality rates varied considerably across centres and those identified as outliers will now need to carefully interrogate local care pathways to understand and address reasons for this, with national policy required to tackle the identified health disparities.