How much will I have if I max out my ISA every year?

Paying £1,666 a month (just under £20,000 a year) into a stocks and shares ISA growing at 5% a year after 0.5% fees could build about £638,350 after 20 years, from £399,840 paid in. At 7% it would be about £796,021. Returns aren't guaranteed.

At 5%, about £250,389 after 10 years and £1,239,472 after 30 years.

Until 5 April 2027, yes. From 6 April 2027, under-65s can only put £12,000 a year into cash ISAs, so the rest would need to go into a stocks and shares ISA to use the full allowance. Over-65s keep the full £20,000 cash limit.

No. The £20,000 allowance resets every 6 April, and anything you don't use is lost.

Most people don't, and smaller amounts still add up. £500 a month into a stocks and shares ISA at 5% growth could build about £191,582 in 20 years, and £1,000 a month about £383,163.

Cash ISAs suit money you might need within about five years, because the balance can't fall. Stocks and shares ISAs have historically grown faster over 10 years or more, but can fall in value. Many people who max out their allowance split it between both. From April 2027 under-65s can put at most £12,000 a year in cash.