These changes to capital gains tax (CGT) are due to come into effect from 6 April 2020, but there will be a consultation on the details first.
From April 2020:
* Lettings relief will only be available to those who are in shared occupancy with a tenant.
* The final period exemption allowing Principle Private Residency exemption for the last 18 months of ownership as long as the property qualified for PRR at some point, will be reduced to 9 months.
* The final period exemption will remain 36 months for those who move into care and for disabled persons.
https://www.gov.uk/government/publications/private-residence-relief-budget-2018-brief