Mr Sunak says government support for the self-employed constitutes an “unprecedented level of support”.
He says ministers have worked to make sure it is “targeted at those who need it the most”.
However, he also has a warning that the government will not be able to “protect every single job or protect every single business”.
The BBC’s Laura Kuenssberg asks what will happen to people not covered by the scheme.
Mr Sunak says it will cover 95% of people who make the majority of their wages through being self-employed.
He says the last 5% have average incomes of £200,000, adding: “It is a very generous scheme and treats them with same parity as the employed.”