An ISA is a type of savings account that can be used to store either cash or investments in a tax-efficient way.
Returns received from cash or investments held in an ISA are paid free of any UK tax.
ISAs have become more flexible over recent years, offering the option to switch holdings within an ISA between cash and investments and to have a mixture of the two. The maximum an individual can pay in total into ISAs each tax year is £20,000. You can normally withdraw money from an ISA at any point, unless you have a fixed term interest product where you have locked away your money in return for a specific interest rate.