No — only a parent or legal guardian can open a Junior ISA. But grandparents CAN contribute to an existing one opened by the parent, and those contributions count toward the £9,000 annual limit. This guide explains exactly how it works, the inheritance tax angles every grandparent should know, and what happens when your grandchild turns 18.
The Rule in One Sentence
Under UK Junior ISA rules, only a person with parental responsibility can be the "registered contact" on a JISA and open the account. Grandparents don't usually have parental responsibility — so they can't open the account, but they can pay into one that already exists.
Who Can Be the "Registered Contact"?
HMRC rules state that the registered contact must be someone with parental responsibility for the child. That's normally:
- The child's mother (automatically)
- The child's father, if he's named on the birth certificate (for births registered after 1 December 2003 in England and Wales) or if he's married to the mother
- A court-appointed legal guardian
- An adoptive parent
- A local authority (for children in care)
Grandparents only have parental responsibility if they have been granted it formally — for example, through a Child Arrangements Order or a Special Guardianship Order. If you're a grandparent who has legally adopted your grandchild, or has been granted parental responsibility by a court, you can open the JISA in exactly the same way a parent would.
For the vast majority of grandparents, opening the JISA is the parent's job. Full stop. HMRC's official guidance is on gov.uk/junior-individual-savings-accounts.
How Grandparents Can Contribute
Once the parent has opened a Junior ISA, anyone can pay into it. The three main routes:
1. One-off bank transfer
The simplest method. The parent gives you the JISA provider's bank details, sort code, account number, and the unique JISA reference. You send money from your own account — the provider applies it to the child's JISA.
Most providers (Hargreaves Lansdown, AJ Bell, Fidelity, Interactive Investor and others) accept third-party contributions by bank transfer.
2. Standing order
Perfect if you want to drip-feed smaller amounts — say, £50 a month for birthdays and Christmas combined. Regular contributions also smooth out market volatility in a Stocks & Shares JISA, because you're buying across a full market cycle.
3. Cheque
Old-school but still accepted by most providers. The cheque must usually be made payable to the provider (not the child) with the JISA reference written on the back.
Always check with the specific provider — a few newer app-based platforms don't accept cheques at all.
How Much Can You Pay In?
The Junior ISA allowance for the 2025/26 tax year is £9,000. This is a combined limit — it doesn't reset for each contributor.
That means if Mum pays in £3,000 and Dad pays in £2,000 this tax year, both sets of grandparents between them can only add another £4,000. If you pay in more than the limit, the excess will be rejected by the provider or, if it slips through, will have to be removed by the parent as the registered contact.
The allowance runs from 6 April to 5 April the following year and doesn't carry over. Use it or lose it.
Inheritance Tax and Gifts to a Junior ISA
This is where grandparents often get tripped up. A contribution to a grandchild's JISA is a gift in the eyes of HMRC, and gifts can have inheritance tax implications.
The good news: several exemptions usually make JISA contributions tax-efficient for larger estates.
Annual exemption — £3,000
You can give away £3,000 per tax year with no IHT implications at all. If you didn't use last year's allowance, you can carry one year's worth forward, so up to £6,000 in a single year. This is per person, not per grandchild — so a couple can give £6,000 combined each year.
Small gifts allowance — £250 per recipient
On top of the £3,000 annual exemption, you can give up to £250 to any number of different people each tax year. You can't use this alongside the annual exemption to the same person, though.
Gifts out of surplus income
This is the underused one. If you make regular gifts from income (not capital), and those gifts don't affect your standard of living, they're immediately exempt from IHT — no 7-year rule, no limit. Monthly standing orders into a JISA can qualify, as long as you document the pattern and your income genuinely covers them. Speak to a qualified adviser if you want to use this seriously.
The 7-year rule
Gifts above the exemptions are "potentially exempt transfers" (PETs). They sit outside your estate as long as you survive 7 years. If you die within 7 years, the gift becomes taxable and is eaten up by the £325,000 nil-rate band (and then taxed at up to 40%).
For a full IHT picture, HMRC's guidance is at gov.uk/inheritance-tax/gifts.
What Happens When the Grandchild Turns 18?
This is the part many grandparents don't realise. On the child's 18th birthday, the Junior ISA automatically becomes an adult Stocks & Shares or Cash ISA in their name. They get full legal control.
That means:
- Neither parents nor grandparents can stop them withdrawing the money
- They can spend it on whatever they like — university fees, a car, a house deposit, or a gap year
- The tax-free wrapper is preserved, so if they leave it invested it continues to grow tax-free
If you're worried about an 18-year-old getting a large lump sum, the main alternatives are a bare trust (child gets full access at 18 too, so similar problem), a discretionary trust (more complex and more expensive), or simply contributing later via smaller gifts once you see how responsible they become. For most families, a Junior ISA is the simplest, most tax-efficient route despite the age-18 handover.
Best Junior ISAs for Grandparent Contributions
Not every provider makes it easy for grandparents to pay in. Look for:
- Clear third-party payment details — some providers bury the bank details deep in the portal
- Standing order support — makes regular giving painless
- Online gift options — Fidelity and Hargreaves Lansdown, for example, offer dedicated gift links
- Low fees — a 0.45% platform fee on a £50,000 balance is £225 a year, so cost matters over 18 years
For a detailed side-by-side of the main UK options, see our Junior ISA comparison, and our Junior ISA guide covers the basics if you or the parents are new to this.
Cash JISA or Stocks & Shares JISA?
Grandparents often lean toward Cash Junior ISAs because "cash is safer". Over an 18-year horizon, that's usually the wrong call. Cash JISAs currently pay around 4–5% interest, which after inflation often means zero or negative real returns. A global tracker in a Stocks & Shares JISA has historically returned around 7% a year on average.
On £9,000 invested per year for 18 years, the difference between a cash rate and a stock-market rate is tens of thousands of pounds by age 18. Capital is at risk — the market can fall sharply in any given year — but 18 years is long enough that the probability of loss is low. For the basics of how this works, see our investing glossary.
FAQ
Can grandparents open a Junior ISA in the UK?
No. Only a parent or someone with legal parental responsibility can open a Junior ISA and act as the registered contact. Grandparents can contribute once the JISA has been opened.
How much can grandparents pay into a grandchild's Junior ISA?
Anyone can contribute, but total contributions across all sources cannot exceed £9,000 in the 2025/26 tax year. That's a combined cap — parents, grandparents and anyone else share the same limit.
Do grandparent contributions to a JISA count toward inheritance tax?
Gifts can be covered by the £3,000 annual exemption, the £250 small gifts allowance, or "gifts out of surplus income". Anything above those limits becomes a potentially exempt transfer and drops out of the estate after 7 years.
Who controls the Junior ISA — the parent or the grandparent?
The registered contact (parent or legal guardian) controls the account, picks investments, and can change providers. Grandparents who contribute have no legal control.
What happens to a Junior ISA when the child turns 18?
It automatically converts into an adult ISA in the child's name. They get full legal control and can withdraw or keep the money invested — the parent and grandparents lose all say.