Chancellor Rishi Sunak will unveil the measures later.
He set out plans for 80% wage subsidies for staff kept on by employers last week - and the PM has said he wants similar protection for freelancers.
However, Boris Johnson added he could not promise the UK would beat the virus "without any kind of hardship at all".
The total number of people in the UK to die with Covid-19, the disease caused by Coronavirus, has reached 465.
Mr. Sunak said last week that the government would cover wages of up to £2,500 a month for staff being kept on by their employer, as part of "unprecedented" measures to prevent workers from being laid off.
The chancellor later said drawing up plans to help self-employed people had proved "incredibly complicated".
Dr. Adam Marshall, director-general of the British Chambers of Commerce, said: "For many people that have seen their businesses disappear in the blink of an eye, things like statutory sick pay or universal credit just isn't enough.
"It doesn't need to be perfect - we just need a system in place," he told the BBC's Today programme.
John Healey, a self-employed driving instructor from Lancashire, said: "We don't need a lot, we just need something.
"But by doing nothing, we just go to the wall, basically," he told the Today programme.
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BBC Newsnight's political editor Nick Watt said all the indications from talking to ministers and Conservative MPs were that the chancellor would match the 80% salary support given to PAYE employees.
He said one minister said the reason why it had taken so long was because it was fiendishly complicated but "when this chancellor acts, he acts big".
BBC business editor Simon Jack said calculating a support wage for the self-employed was so difficult because their income could be lumpy, irregular and intermittent.
Government sources said they had struggled to find a way to avoid paying people who do not need help.
Below is the video of the earlier announcement where the chancellor outlined support for PAYE workers.