Background Interpersonal violence is a major public health concern with alcohol use a known risk factor. Despite alcohol taxation being an effective policy to reduce consumption; Hong Kong, contrary to most developed economies, embarked on an alcohol tax reduction and elimination policy.

Methods To assess the impact of the alcohol tax reductions, we analysed population-based hospitalisation data for assault from the Hong Kong Hospital Authority, and violent and sexual crimes recorded by the Hong Kong Police Force (2004–2018). We conducted an interrupted time series using seasonal autoregressive integrated moving average models on monthly rates. Breakpoints in March 2007 and March 2008 were applied separately.

Results The 2007 tax cut was associated with sustained increases in violence-related hospitalisation rates for 35–49 age group (female: 0.19%, p=0.007; male: 0.22%, p<0.001; overall: 0.16%, p=0.007); and an immediate increase of 51.3% (p=0.005) in the rate of sexual crimes reported. Results for the 35–49 age group after the 2008 tax cut were similar with sustained increases in hospitalisation rates (female: 0.21%, p=0.010; male: 0.23%, p<0.001; overall: 0.17%, p<0.001). The 2008 tax cut was also associated with immediate increases in hospitalisation rates in children (female: 33.1%, p=0.011; male: 49.2%, p<0.001, overall: 31.5%, p=0.007). For both tax cuts, results were insignificant in males and females for other age groups (15–34 and 50+ years).

Conclusions Both alcohol tax reductions in 2007 and 2008 were in some age groups associated with increases in violence-related hospitalisations and reports of sexual assault even in an environment of low crime.