Answers · UK 2025/26

How much could a Junior ISA be worth at age 18 if I pay in the maximum?

Around £290,000 to £320,000 at a 5% return if you pay the full £9,000 a year from birth to 18. The Junior ISA limit is £9,000 for 2026/27, and all growth is tax-free. The child gains access and control of the account at 18.

Last updated: 10 June 2026Last reviewed: 10 June 2026How we verify

Full answer

A Junior ISA (JISA) lets a parent or guardian save up to £9,000 a year for a child for 2026/27, separate from the adult £20,000 allowance. All interest, dividends and capital gains are tax-free, and the child cannot withdraw until they turn 18, when the JISA automatically becomes an adult ISA in their name. Worked example: paying the full £9,000 every year from birth to age 18 contributes £162,000 of your own money. At a 5% average annual return compounded over those 18 years, the pot could be worth roughly £290,000 to £320,000 depending on timing of contributions, with the difference being tax-free growth. Even modest amounts add up: £100 a month (£1,200 a year) from birth at 5% could reach around £35,000 by 18. Two practical points. First, the money legally belongs to the child and they take full control at 18, so they could spend it as they wish. Second, JISA contributions do not reduce your own £20,000 ISA allowance, so a family can shelter £29,000 a year in total across one adult and one child. There is no government bonus on a JISA, unlike a Lifetime ISA. Use the ISA calculator and the compound interest calculator to model contributions and growth rates for your child. Investment values can fall as well as rise; for the Junior ISA rules and limit, see gov.uk.