Children
Junior ISA at 18: what the young adult receives and what changes
A Junior ISA or Child Trust Fund passes to its owner in two steps, at 16 and at 18. This guide follows both, then looks at the choices the rules leave open to a new adult saver, with the tax they would meet outside an ISA.
A Junior ISA turns into an adult ISA automatically on the child's 18th birthday, in the young person's name, and from that day they can take out any of the money. Nothing has to be opened or transferred for the change to happen, and the money already in the account keeps its tax-free status. Two years earlier, at 16, the child can become the registered contact and manage the account, including a change of provider, but cannot withdraw. Child Trust Funds, given to children born between 1 September 2002 and 2 January 2011, follow the same ages: control at 16, access at 18. As an adult, the young person has the full £20,000 ISA allowance for new payments, of which at most £12,000 can go into cash ISAs from 6 April 2027. If £12,000 were moved instead to a taxable account at 4 %, a young adult earning £14,000 would pay £0.00 of tax on the interest in 2027/28.
What a Junior ISA or Child Trust Fund becomes at 18
Interest a year in an adult ISA
£480
| Tax if moved to a taxable account (2027/28) | £0.00 |
| Tax-free interest available to them | £4,570 |
| Room in a cash ISA from 2027/28 | £12,000 |
GOV.UK: Junior ISAs automatically turn into an adult ISA when the child turns 18, and the money can then be taken out.
Sums checked by Radif Partners · Editorial policy · How the sums are done
Two birthdays, two changes
Ownership and control are separate in a Junior ISA. The money belongs to the child from the first payment, but until 16 a parent or guardian with parental responsibility runs the account as its registered contact (GOV.UK, Junior Individual Savings Accounts). At 16, the child can take over that role. From then on they manage the account themselves and, as registered contact, can ask the provider to move it to another provider. What they cannot do is take money out.
At 18 the lock comes off. GOV.UK states that Junior ISAs automatically turn into an adult ISA when the child turns 18, and that the young person can then take out any money in them. If the young person lacks the mental capacity to manage the money at 18, GOV.UK points to a financial deputyship order from the Court of Protection.
Child Trust Funds follow the same ages
A Child Trust Fund was opened for children born between 1 September 2002 and 2 January 2011. Those accounts work in the same way at 16 and 18: the holder can manage the fund from 16 and take the money from 18. A fund that is still open can receive up to £9,000 a year, the same limit as a Junior ISA, and a child cannot hold both at once, so a family that prefers a Junior ISA asks the new provider to transfer the trust fund into it. The youngest Child Trust Fund holders reach 18 on 2 January 2029. GOV.UK has a service to find a Child Trust Fund whose provider is not known, open to parents and to holders aged 16 or over.
The end of the parental rule
Before 18, interest on ordinary savings that a parent gave a child is taxed as the parent's income once it passes £100 a year. That rule applies only to a minor child: section 629 of the Income Tax (Trading and Other Income) Act 2005 defines a minor as a person under 18. Money in a Junior ISA was never caught by the rule (GOV.UK, interest on savings for children). From 18, all of the young adult's interest is their own income, whatever its origin, and is set against their own allowances. The children’s savings tax page explains the rule for the years before.
Leaving the money in the ISA or taking it out
The young adult can leave the matured account as it is, move it to another ISA provider by transfer, or withdraw some or all of it. These choices are not equal in their effect on the ISA wrapper. A transfer between ISA providers keeps the money sheltered and does not use the year's allowance (GOV.UK, transferring your ISA). A withdrawal takes the money out of the wrapper: if it is later paid back into an ISA, it counts as a new payment against that year's allowance, unless the account is flexible and the money is replaced in the same tax year.
From 6 April 2027 that difference weighs more for cash. Under SI 2026/1018, anyone aged 64 or under at the end of the tax year can put at most £12,000 a year into cash ISAs, within the £20,000 total. A matured Junior ISA worth more than that can stay in cash; but once withdrawn, it could take several tax years to put the same sum back into cash ISAs.
| Value withdrawn | Tax years to return it to cash ISAs (from 2027/28) | Tax years at the full £20,000 |
|---|---|---|
| £9,000 | 1 | 1 |
| £15,000 | 2 | 1 |
| £25,000 | 3 | 2 |
| £40,000 | 4 | 2 |
| £60,000 | 5 | 3 |
Tax on the same money outside an ISA
A young adult has the same allowances as anyone else: the Personal Allowance of £12,570, the £5,000 starting rate for savings, reduced by earnings above the Personal Allowance, and the Personal Savings Allowance. With low earnings, a lot of interest can be received tax free in a taxable account. The table shows how much, and what balance at 4 % produces that interest, in 2027/28.
| Earnings | Tax-free interest a year | Balance at 4 % before tax starts |
|---|---|---|
| £0 | £18,570 | £464,250 |
| £14,000 | £4,570 | £114,250 |
| £30,000 | £1,000 | £25,000 |
The position changes as earnings rise. A student with no income can receive far more interest tax free than a young worker on £30,000, whose starting rate has gone and who keeps only the £1,000 allowance. Above it, interest is taxed at 22 % from 6 April 2027 under the Finance Act 2026.
| Money moved out | Interest at 4 % | Tax, no earnings | Tax, earnings £14,000 | Tax, earnings £30,000 |
|---|---|---|---|---|
| £5,000 | £200 | £0.00 | £0.00 | £0.00 |
| £12,000 | £480 | £0.00 | £0.00 | £0.00 |
| £20,000 | £800 | £0.00 | £0.00 | £0.00 |
| £40,000 | £1,600 | £0.00 | £0.00 | £132.00 |
The tax figures are for one year. They change each year with the young adult's earnings, and the protection of the ISA, once lost, does not come back on its own: only new payments, within the limits of each year, can restore it.
A worked example
Take a cash Junior ISA worth £15,000 on its owner's 18th birthday in June 2027. Left in place at 4 %, it pays about £600 of interest a year, all of it tax free, and the young adult still has £12,000 of cash ISA room for new savings in 2027/28. Suppose £5,000 is taken out for the costs of a first year of study. The other £10,000 stays sheltered. If the £5,000 is not spent and the account is not flexible, putting it back into a cash ISA later counts against the £12,000 of the year in which it is paid in, alongside any other saving that year.
For a stocks and shares Junior ISA, the change at 18 does not alter the investments, which can rise or fall in value as before. One rule of the reform matters here: from 6 April 2027, interest on cash held inside a stocks and shares ISA bears a flat charge at the savings basic rate of 22 %, paid by the ISA manager. A young adult who sells investments and leaves the proceeds as cash in that account meets this charge, whatever their own tax position.
A young adult living in Scotland meets the same figures. Scottish income tax rates apply to wages and other non-savings income, but interest is taxed at the UK savings rates and bands, so the tables above hold for a saver anywhere in the UK, at least for the interest itself.
New accounts open at 18
Turning 18 also opens adult accounts to the young person. Since 6 April 2024 adult cash ISAs can only be opened from 18; before that birthday a Junior ISA is the only ISA available to them. From 18 they can also open a Lifetime ISA, which adds a 25 % bonus on up to £4,000 a year for a first home or for age 60 (GOV.UK, Lifetime ISA). Those £4,000 count inside the £20,000 allowance like any other payment.
How many accounts reach this point
HMRC counted 1,600,000 Junior ISAs subscribed to in 2024/25, with an average payment of £1,570. Each year a new group of those accounts reaches 18 and passes to its owner, together with the Child Trust Funds of children born up to January 2011. Among adult ISAs subscribed to in the same year, 64 % were cash accounts, out of 16,800,000 in all, the type of account to which the £12,000 limit applies from 6 April 2027 (HMRC annual savings statistics, September 2026). The Junior ISA page shows what regular payments grow to before that birthday.