A Lifetime ISA is a government-backed saving scheme to help people save for buying their first home or for retirement. When saving using a Lifetime ISA (LISA) the government will contribute a 25% bonus up to a certain limit (currently up to a maximum of £1,000 a year.)
This can be opened between the ages of 18 and 40 and you are able to contribute up to £4,000 per tax year to your LISA. Each tax year runs from 6th April-5th April the following year.
You are able to have a Help to Buy ISA and Lifetime ISA, but cannot use both for the purchase of your first home.
You can use the savings in your Lifetime ISA as your deposit for your Gen H Mortgage. You are also able to use multiple Lifetime ISAs on one mortgage application.
You can find more information on Lifetime ISAs here