Chancellor Rishi Sunak is facing calls to extend the scheme to support self-employed workers throughout the coronavirus crisis.
A cross-party group of 113 MPs wrote to Mr Sunak on Thursday, warning many will not be able to return to work despite easing of lockdown restrictions.
The MPs said those workers, who include many plumbers, builders and hairdressers, "will be left without work and without support" if the Self-Employment Income Support Scheme (SEISS) is not extended past Sunday, May 31.
Mr Sunak extended the Coronavirus Job Retention Scheme earlier this month until the end of October preventing mass redundancies across the country for UK workers.