Just released on government website:
Top points are:
Individuals should not contact HMRC now. HMRC will use existing information to check potential eligibility and invite applications once the scheme is operational.
HMRC will use the average trading profits from tax returns in 2016-17, 2017-18 and 2018-19 to determine the size of the grant. The scheme will be open to those with a trading profit of less than £50,000 in 2018-19 or an average trading profit of less than £50,000 from 2016-17, 2017-18 and 2018-19.
The income support scheme, which is being designed by HMRC from scratch, will cover the three months to May. Grants will be paid in a single lump sum instalment covering all 3 months, and will start to be paid at the beginning of June.