Unveiling the plans at the daily Downing Street press conference, Mr Sunak told hairdressers, childminders and cleaners concerned about losing their livelihoods: “You have not been forgotten”.
Mr Sunak said: “To support those who work for themselves, today I am announcing a new self-employed income support scheme.
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“The government will pay self-employed people who have been adversely affected by the coronavirus a taxable grant worth 80 per cent of their average monthly profits over the last three years, up to £2,500 a month.”
Mr Sunak described the offer, which is open to people with trading profits of up to £50,000, as “one of the most generous in the world”.
Only those who are already in self-employment who have a tax return for 2019 will be able to apply, with HMRC ordered to contact people directly if they are eligible.
The scheme will be open for at least three months and will begin “no later than the beginning of June”, Mr Sunak said.
Those who are struggling right now can access business interruption loans, and self-assessment income tax payments can be deferred until the end of January, he added.
The chancellor also hinted that the self-employed could lose tax breaks as a result from the state support handed to them to survive the coronavirus outbreak.
“I must be honest and point out that in devising this scheme in response to many calls for support, it is now much harder to justify the inconsistent contributions between people of different employment statuses,” Mr Sunak said.
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“If we all want to benefit equally from state support, we must all pay in equally in future.”
Mr Sunak warned that the government could not protect every single job or business but measures were in place to ease the burden on millions of people.
The packaged was widely welcomed by business groups and union leaders but the June start date sparked a backlash, with warnings that people could not wait months for help.
Labour MP Stephen Doughty said: “What are millions of people supposed to do until June, not least when there’s a five-week wait for universal credit? How do they put food on table and pay their bills?
“This is a big announcement but with a huge sting in the tail for millions of self-employed and freelancers.
“The government must urgently bring this scheme forward much more sooner so that livelihoods are not put at risk.
“Most people simply don’t have the cash reserves in their bank accounts to get through one month, let alone three – and not least while banks have just racked up overdraft charges.”
Liberal Democrat MP Layla Moran said: “An 80 per cent grant for the self-employed is a welcome measure. However, after days of anxious uncertainty, there are still many unanswered questions for people who are already struggling to put food on the table and look after their families.
“Having to wait until early June does not give self-employed people parity with those in full-time work.”
Dame Carolyn Fairbairn, director general of the CBI, said: “These new measures will provide essential support to those facing significant uncertainty and loss of income.
“Given the complexity of the task, it’s understandable this will take time to deliver. Fast clarity on how and when money will reach their bank accounts will help individuals to plan.”
TUC general secretary Frances O’Grady said it was a “welcome step”, but added: “It’s vital that support reaches workers as soon as possible. Many are already dealing with severe hardship.”