Millions of self-employed people whose business has been affected by coronavirus can apply for grants from the government from Wednesday.
The Self Employed Income Support Scheme is designed to match the support being given to furloughed employees.
The grants will be calculated as 80% of average monthly profit over a period of up to three years.
The government said the money will be paid into the accounts of eligible people six days after applying.
The maximum payment will be £7,500, intended to cover March, April and May.
The scheme is the biggest direct financial support package for freelancers and the self-employed since lockdown started.
It was unveiled in March after the government faced criticism for failing to provide support for self-employed and freelance workers in its earlier package of economic measures.
Launching at 08:00 on Wednesday, the process will be run by HM Revenue & Customs, which has been operating and overseeing loan schemes and the government's furlough payments.
Those able to make a claim have already been contacted by HMRC and can use a unique reference to make their claim.
But those who started in business from early April last year will miss out, as will those who pay themselves just with dividends from a limited company.
Derek Cribb, chief executive of the Association of Independent Professionals and the Self-Employed, said: "For the self-employed, coronavirus
is not only a health crisis, but also a pressing income crisis.
"We are delighted that the government has heeded much of IPSE's advice by setting up the Self-Employment Income Support Scheme, which extends a much-needed lifeline to those self-employed people who are eligible for it."
The government has not said whether the initiative will be extended into the autumn in line with the furlough scheme, which protects 80% of employees' wages up to £2,500 a month.
On Tuesday, Chancellor Rishi Sunak announced that scheme was being extended until the end of October.
Mr Sunak said: "With payments arriving before the end of this month, the self-employed across the UK will have money in their pockets to help them through these challenging times."