Reviewed by Mustafa Bilgic
Founder, WebCalculator
The £9,000 Junior ISA allowance is taken from GOV.UK for the 2026/27 tax year. Growth projections are illustrative and not guaranteed — estimates only, not financial advice.
A Junior ISA grows tax-free until your child turns 18 — a powerful head start. Enter a starting amount, monthly contribution and the years to 18 to see the pot they could unwrap on their eighteenth birthday.
Tax-free · £9,000 annual allowance
A Junior ISA (JISA) is a long-term, tax-free savings account for under-18s. A parent or guardian opens it, but anyone — grandparents, family, friends — can pay in, up to a combined £9,000 a year. All interest and investment growth is free of Income Tax and Capital Gains Tax, and the money is locked away until the child turns 18.
| Monthly saving | Pot at 18 (from birth, 5%) |
|---|---|
| £25 | ~£8,800 |
| £50 | ~£17,600 |
| £100 | ~£35,200 |
| £250 | ~£87,900 |
A child can hold a cash JISA, a stocks-and-shares JISA, or one of each, as long as total contributions stay within £9,000. Over an 18-year horizon, a stocks-and-shares JISA has historically outpaced cash, though values can fall as well as rise. Compare general tax-free growth on the ISA calculator and the maths of compounding on the compound interest calculator.
£9,000 a year, across all of the child's Junior ISAs combined. The money grows completely tax-free.
At 18, when it becomes an adult ISA and the child gains full control — to withdraw tax-free or keep invested.
Saving £100 a month from birth at 5% could build a pot of around £35,000. Maximising the £9,000 allowance could reach six figures, all tax-free.
Anyone — parents, grandparents, family and friends — as long as the combined total stays within the £9,000 annual limit. Only a parent or guardian can open and manage it.