Chancellor Rishi Sunak is to set out details of how employers will be asked to help pay the wages of furloughed workers.
The government is paying 80% of workers’ salaries up to £2,500 a month for some 8.4 million workers under its furlough scheme.
The Treasury has not denied reports that firms will be asked to contribute about 20% of wages from August.
Ministers previously announced that the scheme will be extended to October.
The chancellor said earlier in May that the government will provide the same level of earnings, but that it will ask companies to “start sharing” the cost of the scheme from August.
It is thought that employers could also be asked to cover National Insurance and pension contributions for furloughed workers from August.
Mr Sunak is due to lead Friday’s daily Downing Street press briefing to outline changes to the scheme.
The furlough scheme, aimed at mitigating the economic effects of the coronavirus pandemic, was originally intended to last until the end of July. Officially called the Coronavirus Job Retention Scheme, it has since been extended until the end of October.
Employers’ claims under the scheme have reached £15bn.