What is Junior ISA Calculator?
A Junior ISA Calculator computes junior isa from the inputs you provide. It applies the standard formula to the values you enter and returns the result instantly, without sending any data to a server. Limit £9,000 / year (2024-25 and 2025-26).
Junior ISA Calculator
Project the value of a Junior ISA at age 18. Uses the 2024-25 + 2025-26 limit of £9,000 a year, tax-free growth, and your chosen rate of return. Year-by-year breakdown.
A Junior ISA grows tax-free until the child turns 18, when they get full control. £9,000 a year from age 5 at a 7% annual return projects to roughly £155,000 at age 18. Even £100 a month from birth can pass £30,000 by 18.
Inputs
How to use it
- Enter the child age now (0 to 17). Compounding has 18 minus age years to run.
- Enter the annual contribution. The 2024-25 and 2025-26 JISA limit is £9,000 across cash JISA and stocks-and-shares JISA combined.
- Add any existing pot if the child already has a JISA or transferred Child Trust Fund.
- Pick an expected annual return. UK equities have averaged roughly 5% to 7% real over long periods. Cash JISAs return roughly 4% to 5% (2024-25 best buys).
- Hit Calculate and read the year-by-year balance to see compounding in action.
About this calculator
Junior ISAs (JISAs) were introduced in 2011 to replace Child Trust Funds. There are two types: cash JISA (interest, FSCS protected) and stocks-and-shares JISA (invested, market-linked). The annual contribution limit applies across both combined and is £9,000 for both 2024-25 and 2025-26.
A parent or guardian opens the account and is the registered contact. Anyone (parents, grandparents, friends) can pay in. The child gets read-only access at 16 and full control on their 18th birthday, when the JISA converts to an adult ISA. The child can choose to keep, transfer, or withdraw the entire pot.
Returns inside a JISA are completely free of UK income tax and Capital Gains Tax. The compounding effect over 18 years is significant: starting at birth at 7% annual returns, a £9,000 yearly contribution projects to roughly £320,000 at age 18, of which over £150,000 is investment growth.
Real-world use cases
Saving for university
A full pot at 18 can cover undergraduate maintenance + a deposit on a flat. JISAs are the most tax-efficient wrapper for this goal.
First home deposit
At 18 the JISA converts to an adult ISA. Combined with a Lifetime ISA from age 18, the child gets a 25% government bonus on up to £4,000 of additional savings each year.
Grandparent gifting
JISA contributions count as gifts for inheritance tax. £9,000 a year falls under the annual exemption + normal-expenditure-out-of-income rules. Tax-efficient legacy planning.
Compound interest education
Show kids the power of long-term investing with a real example. £100 a month from age 0 at 7% lands at over £45,000 by 18.
What it handles
- Cash JISA and stocks-and-shares JISA (combined limit).
- Custom return rate, current age, existing balance.
- Year-by-year compounding table.
- Annual or monthly contribution patterns (annual amount = monthly * 12).
What it does NOT handle
- Inflation adjustment - figures are nominal pounds.
- Charge / platform fee impact on returns.
- Mid-year contribution timing (assumes start of year).
- Tax on the parent for transferred Child Trust Funds.
Common mistakes
- Mixing up the £9,000 limit with the adult ISA £20,000 limit. The JISA is much smaller.
- Believing the parent owns the money. They do not. At 18 the child gets full legal control.
- Assuming returns. 7% is a long-run equity assumption, not a guarantee. Cash JISAs are nearer 4% to 5%.
- Forgetting Child Trust Fund transfers count toward the £9,000 only when newly contributed.
Frequently asked questions
What is the Junior ISA limit for 2025-26?
The Junior ISA contribution limit for the 2025-26 tax year is £9,000, the same as 2024-25. This is the combined cap across cash JISA and stocks-and-shares JISA.
Who can pay into a Junior ISA?
Anyone can contribute - parents, grandparents, godparents, family friends. The total annual amount across all contributors must stay within the £9,000 limit. Only a parent or legal guardian can open the account.
When does the child get the money?
On their 18th birthday the JISA converts automatically to an adult ISA in the child’s name. They can keep it, transfer it, or withdraw the whole pot - it is legally theirs and there is no parental veto.
Are Junior ISA returns really tax-free?
Yes. All interest (cash JISA) and all capital gains + dividends (stocks-and-shares JISA) are exempt from UK income tax and Capital Gains Tax for the entire life of the JISA, both before and after the child turns 18.
What happens to a Child Trust Fund?
Child Trust Funds (CTFs) were closed to new accounts in 2011. Existing CTFs can be transferred to a Junior ISA at any time and the transfer does not use up the £9,000 annual limit.
Cash JISA vs stocks-and-shares JISA - which is better?
Over an 18-year horizon, stocks-and-shares JISAs have historically outperformed cash by a wide margin. Cash JISAs offer FSCS protection and zero volatility but typically return 4% to 5%, vs 5% to 7% real for global equity index funds. The longer the horizon, the more equities tend to win.
Can I withdraw money from my child’s JISA?
No. Once paid in, the money is locked until the child turns 18. The only exception is if the child has a terminal illness diagnosis. There is no early-withdrawal penalty - early withdrawal is simply not allowed.
How does a JISA fit with inheritance tax planning?
JISA contributions are gifts. They fall within the £3,000 annual exemption or the normal-expenditure-out-of-income rule, both of which avoid the 7-year rule. Grandparents commonly use JISAs as a tax-efficient way to pass on wealth.