We analyze the impact of Covid-19 on productivity in the United Kingdom using data derived from a large monthly firm panel survey. Our estimates suggest that Covid-19 will reduce TFP in the private sector by up to 5% in 2020 Q4, falling back to a 1% reduction in the medium term. Firms anticipate a large reduction in ‘within-firm’ productivity, primarily because measures to contain Covid-19 are expected to increase intermediate costs. The negative ‘within-firm’ effect is partially offset by a positive ‘between-firm’ effect as low productivity sectors, and the least productive firms among them, are disproportionately affected by Covid-19 and consequently make a smaller contribution to the economy. In the longer run, productivity growth is likely to be reduced by diminished R&D expenditure and diverted senior management time spent on dealing with the pandemic.