Junior ISA Calculator 2026/27
Project a child's JISA pot at age 18 with a £9,000 annual limit, tax-free growth, and the magic of long compounding.
Last updated: May 2026 · 2026/27
JISA setup
13 years to age 18 (when the pot becomes theirs).
Annual: £1,200 (limit £9,000/year).
Type & return
Global equity historical real return ~6-7% nominal long-term.
Pot at age 18
£25,722
£16,600 contributed + £9,122 tax-free growth
Year by year
About Junior ISAs
A Junior ISA is a tax-free savings or investment account for under-18s. Anyone can pay in (parents, grandparents, friends) up to the annual limit of £9,000.
- The child can't access the money until age 18 (then it becomes theirs unconditionally).
- Two types: Cash JISA (fixed-rate savings) and Stocks & Shares JISA (investments).
- You can split contributions across both types in the same tax year, up to the £9,000 total.
- Only one Cash JISA and one S&S JISA per child at a time.
- At 16-17 the child can also open an adult Cash ISA on top.
For a JISA opened at age 0, the money is locked away for 18 years. That's long enough that historical equity returns (~6-7% nominal, after CPI ~3-4% real) overwhelm any short-term volatility.
At 4% cash vs 7% equity over 18 years, £100/month grows to roughly £31k vs £43k respectively — a £12k difference, all of it tax-free. The shorter the time horizon, the smaller the case for equities.
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