More than 110,000 self-employed people whose businesses have been hit by coronavirus have already applied for government grants.
Wednesday marked the first day of the scheme’s operation and officials said the value of the claims made so far is more than £340m.
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.
It is hoped that money would 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.
The process is being run by HMRC, which has been operating and overseeing loan schemes and the government’s furlough payments.
Most of the 3.5 million people affected should have been contacted, the MHRC said, and invited to get ready to make a claim by using its eligibility checker.
They will then have been given a time at which to apply, before 18 May, although if applicants are unable to file at that time HMRC says they can still go ahead and apply.
Derek Cribb, chief executive of the Association of Independent Professionals and the Self-Employed, said the scheme extended “a much-needed lifeline to those self-employed people who are eligible for it”.
He said: “For the self-employed, coronavirus is not only a health crisis, but also a pressing income crisis, until now they’ve been coping either by applying for Universal Credit or by digging into their savings.”