Although it was a record collapse of the UK economy, the decline was slightly smaller than first estimated.
The Office for National Statistics (ONS) said that the initial estimate in the three months to June was of a quarterly 20.4 percent crash.
Though the British economy slightly missed estimates, the economic downturn is still more than any other major advanced economy.
The fall was the biggest since the ONS records began in 1955. Other data have suggested Britain is on course for its biggest annual fall since the 1920s.
The UK economy had already shrunk by 2.5 percent in the January-March period as the country entered lockdown in late March.
Output has rebounded in recent months but the recovery looks to be fading with rising coronavirus cases and forecasts of a jump in unemployment as the government scales back job support.
"The renewed Covid-19 restrictions will probably mean that GDP stagnates in Q4, leaving economic activity marooned 5.5 percent short of its pre-crisis level," Ruth Gregory of consultancy Capital Economics said.