In the 2019/20 tax year, the ISA allowance is £20,000. You can choose to use your ISA allowance in a cash ISA, a stocks & shares ISA, an innovative finance ISA, a lifetime ISA (which has a lower limit of £4,000) or any combination of the four, as long as you don't exceed the annual allowance. This means that the most you can pay into a cash ISA in any tax year is £20,000; if you do this, you will not be able to put any money into any of the other types of ISA. You must pay your money in before 5 April 2020 if it is to count towards the annual ISA limit for the 2019/20 tax year.
Since the introduction of the Personal Savings Allowance in April 2016, which allows basic rate taxpayers to earn £1,000 of savings income tax-free (£500 for higher rate taxpayers), questions have been raised over the value of using an ISA for savings. However, for the vast majority of savers, making use of their ISA allowance still makes sense. This is because:The tax benefits in an ISA are cumulative, meaning you can shelter ever larger sums from tax year-on-year.
While the Personal Savings Allowance is currently adequate for most savers to avoid paying tax on their savings without using an ISA, savings rates will not have to rise too much further before tax may become an issue. For instance, if rates were to reach 5%, non-ISA balances of £20,000 and over would become taxable for basic rate taxpayers (£10,000 and over for high rate taxpayers).
If the Government were to review the way savings are taxed in the future, the Personal Savings Allowance seems far more vulnerable to change than the more established ISA regime. It would be extremely difficult to justify the removal of tax advantages from money already held in ISAs compared to lowering or even scrapping the Personal Savings Allowance.