Common Junior ISA mistakes (and how to avoid them)

Opening a Junior ISA is one of the best things you can do for your child's future. Between choosing the type, the provider and the investments, though, there are a few easy slips to make.

The good news is that most are simple to avoid once you know about them. Here are the common ones.

Quick summary: the most common mistakes are choosing cash for money that won't be needed for years, paying more in charges than you need to, going over the £9,000 limit, leaving money uninvested, and not talking to your child about their money.

The figures below use 6% a year for investments and 3% for cash. They're illustrations: real returns go up and down and nothing is guaranteed.

1. Choosing cash for a long time frame

The mistake: opening a cash Junior ISA when the money won't be needed for 10 years or more.

Why it matters:

A newborn's Junior ISA has 18 years ahead of it. Over periods that long, investments have historically grown much more than cash.

Example:

£200 a month for 18 years in cash at 3%: about £57,000
£200 a month for 18 years invested at 6%: about £76,500
A difference of around £19,500

What to do instead:

For long time frames, many families choose a stocks and shares Junior ISA. The value will go up and down along the way, but with 18 years there's time for the ups and downs to even out.

When cash makes sense:

The money is needed for something specific at 18, and that's fewer than about five years away
Any fall in value would really worry you

Our stocks and shares vs cash comparison goes into more detail.

2. Paying more in charges than you need to

The mistake: choosing expensive funds or platforms without noticing the long-term cost.

Why it matters:

A difference of a fraction of a percent a year doesn't sound like much. Over 18 years, it adds up.

Example (£200 a month for 18 years, 6% before charges):

With 0.15% a year in charges: about £75,400
With 1.00% a year in charges: about £69,300
About £6,100 lost to charges

Common traps:

Active funds charging 0.75% or more, when index funds covering the same market charge 0.1% to 0.25%
Paying a percentage platform fee when some platforms charge nothing on Junior ISAs
Paying dealing charges on regular monthly payments

What to do instead:

Look at the total cost: platform fee plus fund charge
Consider a low-cost index fund
Check whether your platform charges for regular investing
See our Junior ISA providers guide for current charges

3. Letting allowance you meant to use slip by

The mistake: planning to pay in more this year, then running out of time.

Why it matters:

The £9,000 allowance runs from 6 April to 5 April. Anything unused is gone: you can't carry it forward.

You don't need to fill it. Most families pay in far less than £9,000, and that's fine. This is only about money you'd planned to put in and didn't get round to.

What to do instead:

Work out what you can comfortably afford
Set up a monthly direct debit for that amount
Have a quick look in March: if you'd like to top up, do it before 5 April
If grandparents like to give money at birthdays or Christmas, they can pay it straight in

Our contribution limits guide explains the rules.

4. Going over the £9,000 limit

The mistake: several family members paying in without keeping track, and the total going over £9,000.

Why it matters:

Providers normally turn away payments over the limit for their own account. But if a child has two Junior ISAs (one cash, one stocks and shares), each provider may not know about the other, and the total can go over. That then has to be put right, which is a hassle.

Example:

Parents pay in £400 a month: £4,800 a year
One set of grandparents gives £3,000 at Christmas
The other gives £2,000 on their birthday
Total: £9,800, which is £800 over

What to do instead:

Keep a running total through the year
Tell family roughly how much room is left
Check the year-to-date total on your provider's app
If it happens, contact the providers straight away

One family message at the start of each tax year usually sorts it.

5. Leaving money uninvested

The mistake: paying money into a stocks and shares Junior ISA but not choosing an investment.

Why it matters:

On some platforms, paying in and investing are two separate steps. Skip the second, and the money sits as cash, earning little or nothing, while you think it's invested.

Example:

A parent pays in £9,000 in April
Forgets to choose a fund
Finds it still sitting as cash a year later
At 6%, that's around £540 of growth missed

What to do instead:

Log in a day or two after your first payment
Check the money shows as invested in a fund, not "cash" or "pending"
For regular payments, check the first month goes into the fund, then look now and then

Most platforms invest regular payments automatically once set up, but it's worth checking.

6. Too many funds

The mistake: buying 10 or 15 funds on the idea that more is safer.

Why it matters:

One global index fund already holds thousands of companies in dozens of countries. More funds mostly means overlap, more to keep track of and sometimes higher charges.

An over-complicated example:

UK large companies (20%)
UK smaller companies (10%)
US large companies (15%)
US smaller companies (5%)
Europe (10%)
Asia (10%)
Emerging markets (10%)
Global (20%)

That's eight funds with a lot of overlap. The global fund already contains most of what the others hold.

What to do instead:

For many families, one global index fund is enough, such as:

the Vanguard FTSE Global All Cap Index Fund, or
the Fidelity Index World Fund

Squids-In is independent, and we don't earn anything from any fund or provider we mention.

When more than one makes sense: if you'd like a UK tilt, or some bonds. Even then, two or three funds is plenty.

Our index funds guide compares some options.

7. Paying for an active fund without a good reason

The mistake: choosing an expensive active fund because it did well last year, or has good marketing.

Why it matters:

Most active funds do worse than their index over 15 years or more, once their higher charges are taken off.

Example (£200 a month for 18 years, 6% before charges):

Active fund charging 0.75%: may or may not beat the index
Index fund charging 0.15%: follows the market
The difference in charges alone: about £3,700

What to do instead:

Start from low-cost index funds, and only pay more if you have a clear reason.

Why index funds work well:

They follow the market, up and down
They cost a fraction of an active fund
They don't depend on one manager's calls
They're spread out automatically

8. Paying in by hand

The mistake: relying on remembering to transfer money each month.

Why it matters:

Life gets busy. You miss a month, then another.

What to do instead:

Set up a direct debit for an amount you're comfortable with
Pick a date just after payday
Let it run

A bonus: investing the same amount each month means you buy more when prices are low and less when they're high.

Look once a year: check it's working, and otherwise leave it alone.

9. Waiting to start

The mistake: putting it off until your child is 5, 10 or 15.

Why it matters:

Growth needs time. The earlier money goes in, the longer it has to grow.

Example (at 6% a year):

£200 a month from birth to 18: about £76,500 (£43,200 paid in)
£200 a month from age 10 to 18: about £24,500 (£19,200 paid in)

The money paid in during the early years has the longest to grow, so it does the most work.

What to do instead:

Start when you can, even with a small amount. You can always increase it later.

10. Not talking to your child about it

The mistake: treating the Junior ISA as a secret your child only finds out about at 18.

Why it matters:

A Junior ISA is a great teaching tool. At 18 the money is theirs to use however they like. A young person who understands how it grew, and what it could still do, is much better placed to make a good choice with it.

What you can do:

Ages 5-9:

"We're saving money for your future in a special account"
Show them the balance once or twice a year
"It's growing for when you're older"

Ages 10-14:

Explain compound growth with simple examples
Try the Time Machine in the Squids-In app, or our Junior ISA calculator, together
Look at the account together now and then

Ages 15-17:

From 16 they can take control of how it's invested, so involve them
Talk about what the money might be for
Explain that at 18 it becomes an adult ISA, and it can stay invested
Talk through taking money out versus leaving it to grow

Squids-In is built for this: 130 short lessons for children aged 10 and up, and the Island Market, a game where they can try investing with pretend money first.

11. Checking too often

The mistake: logging in every week, or every day, to see how it's doing.

Why it matters:

Short-term ups and downs are normal. Watching them closely makes it tempting to act on them, such as selling after a fall.

How it tends to go:

Markets rise: you feel good
Markets fall 10%: you wonder about selling
You sell, markets recover, and the fall becomes a real loss

An example: in early 2020, as COVID spread, global shares fell by about a third in a few weeks. A global index fund was back above its earlier level before the end of the year. Anyone who sold in March missed that recovery. (Not every fall recovers that quickly; some have taken years.)

What to do instead:

Look once a year, perhaps in March or April when you review payments
Try not to act on news about crashes or rallies
Remember how many years there are to go

A useful line: "Time in the market beats timing the market."

12. Never reviewing your provider

The mistake: opening a Junior ISA years ago and never checking whether the charges still compare well.

Why it matters:

Charges change. Several platforms now charge no account fee at all on Junior ISAs, which wasn't the case a few years ago.

Example:

A Junior ISA opened years ago with a 0.45% platform fee
The same fund could now be held with no platform fee elsewhere
On a £30,000 balance, that's £135 a year, every year

What to do instead:

Every couple of years:

Check the total cost (platform plus fund)
Compare with current options
If moving would save a meaningful amount, ask the new provider to transfer it (transfers are usually free and take a few weeks)

Our providers guide has current charges.

A quick checklist

✅ For 10 years or more, consider stocks and shares

✅ Check the total cost: platform fee plus fund charge

✅ Keep it simple: one or two low-cost index funds

✅ Set up a monthly direct debit

✅ Pay in what you can comfortably afford

✅ Keep track if several people pay in

✅ Check the money is actually invested

✅ Start as early as you can, even with a little

✅ Look once a year, not every week

✅ Talk to your child about it

✅ Review your provider every couple of years

✅ Try not to sell in a panic when markets fall

Key points

Cash for long time frames has historically grown much less than investments
Charges add up: a difference under 1% a year can cost thousands over 18 years
Keep an eye on the total if several people pay in
Check the money is invested, not sitting as cash
One global index fund is enough for many families
Starting earlier gives the money more time
Talking to your child prepares them for the day it's theirs
Checking less often makes it easier to stay calm