The UK government determines the maximum amount you can invest in Individual Savings Accounts (ISAs) annually. It has been set at £20,000 for the 2021/2022 tax year, just like in every year since 2017. This is known as the ISA allowance. The limits are set for all ISAs combined, not for individual accounts, so you can have several different types of accounts at one provider in the same year, all within the same ISA wrapper.
For example, you can save £12,000 in a cash ISA, £3,000 in a stocks and shares ISA, £1,000 in an innovative finance ISA, and £4,000 in your Lifetime ISA in the same tax year. Be aware however that the maximum you can invest in your Lifetime ISA is £4,000 per tax year.
However, you don’t need large sums to start an ISA: some providers will allow you to open an ISA with as little as £1.
It is important to keep in mind that any unused allowance does not roll over to the next tax year, so if you don’t use it, you will lose it. You will get a new allowance on 6 April of each year, the start of the new tax year, but you will not be able to add any money to the old ISA from the previous tax year.