Your annual ISA allowance is £20,000. This is how much you can save tax-free in ISAs each tax year (from 6th April to 5th April), and it's set by the UK government.  

Your ISA allowance resets at the start of a new tax year, on April 6th. Bear in mind that you can’t carry any unused allowance over to the next tax year. So, if you don't use your allowance, you’ll lose it.