In October, the government will reduce its contributions further to cover 60 per cent of wages at a cap of £1,875. Employers will be required to pay the remaining 20 per cent.
The Treasury said the average cost to employers would equate to 5 per cent of gross employment costs in August, 14 per cent in September and 23 per cent in October.
Mr Sunak said the furlough and self-employment schemes had been a "lifeline" for millions of people and businesses.
The chancellor added: "We stood behind Britain’s businesses and workers as we came into this crisis, and we stand behind them as we come through the other side.
"Now, as we begin to re-open our country and kickstart our economy, these schemes will adjust to ensure those who are able to work can do so, while remaining amongst the most generous in the world."
The comments came as the Treasury renewed its promise that HMRC would "not hesitate" to take action against those found to be abusing the schemes.
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