No more payments can be made into your investment ISA, but it’ll keep its tax benefits - so any interest, dividends or investment growth after the date of death will continue to be tax free - until the first of any of the following events happens:
the investment ISA is closed
the administration of your estate is completed
three years after your death
Your investment ISA will then be paid out according to instructions from the people dealing with your estate.
If you have a spouse or civil partner, they will receive an additional ISA allowance on top of their normal £20,000. The value of the additional allowance will be equal to the value of your investment ISA at the date of your death or at the point you ISA is closed – whichever is higher. If they are due to inherit any of the cash or investments from your ISA, they may be able to pay them into their own ISA using that extra allowance.