Can I open a Lifetime ISA if I already have an ISA(s)?
Under existing ISA rules, you can pay into one of each kind of ISA per tax year (so a cash ISA – this includes a Help To Buy ISA, a Stocks & Shares ISA and a Lifetime ISA). The limit for the Lifetime ISA is £4,000 per tax year and the total, overall ISA limit is £20,000 for the tax year of 2019/20.