BACKGROUND: Exposure to SARS-CoV-2, subsequent development of COVID-19 and death from COVID-19 may vary by occupation, and the risks may be higher for those categorised as 'essential workers'. METHODS: We estimated excess mortality by occupational group and sex separately for each month in 2020 and for the entire 12 months overall. RESULTS: Mortality for all adults of working age was similar to the annual average over the previous 5 years. Monthly excess mortality peaked in April, when the number of deaths was 54.2% higher than expected and was lowest in December when deaths were 30.0% lower than expected.Essential workers had consistently higher excess mortality than other groups throughout 2020. There were also large differences in excess mortality between the categories of essential workers, with healthcare workers having the highest excess mortality and social care and education workers having the lowest. Excess mortality also varied widely between men and women, even within the same occupational group. Generally, excess mortality was higher in men. CONCLUSIONS: In summary, excess mortality was consistently higher for essential workers throughout 2020, particularly for healthcare workers. Further research is needed to examine excess mortality by occupational group, while controlling for important confounders such as ethnicity and socioeconomic status. For non-essential workers, the lockdowns, encouragement to work from home and to maintain social distancing are likely to have prevented a number of deaths from COVID-19 and from other causes.