Best Cash ISA apps UK: rates and flexibility compared

By ChrisLast updated 16 October 2026

The highest headline Cash ISA rates from apps all come from 12-month bonuses, so compare the rate underneath too. Chip’s Smart Cash ISA pays 4.68% AER for 12 months, then 3.50% AER and is flexible. Trading 212 pays a steady rate with no bonus, and Monzo is the only one with a fixed rate.

The short answer

If you want a high rate for the first year, an easy app and the freedom to take money out and put it back, Chip’s Smart Cash ISA is our pick. If you want the best rate over the long run without watching the calendar, Trading 212’s Cash ISA pays more than Chip’s standard rate. If you want certainty, Monzo’s fixed Cash ISA Pot locks in a rate for a year.

Chip Smart Cash ISA: 4.68% AER for 12 months, then 3.50% AER. Flexible, unlimited withdrawals.
Plum Cash ISA: 4.73% AER variable for 12 months, then 2.54%. Flexible, but the bonus has conditions.
Moneybox Cash ISA: 4.72% AER variable for 12 months, then 3.45%. Needs £500 and few withdrawals.
Trading 212 Cash ISA: 3.6% AER variable, flexible. No bonus to expire.
Monzo Fixed Rate Cash ISA Pot: 4.70% AER fixed for 1 year.
Chase: no Cash ISA at all.

How Cash ISA boosts work

Almost every app ISA with an eye-catching rate is made of two parts: a standard variable rate and a bonus on top for the first 12 months. When the bonus ends, you drop to the standard rate. The bonus is the marketing; the standard rate is what you will live with.

The size of the bonus varies a lot. Chip’s is 1.18% AER. Plum’s is 2.19%, and Moneybox’s is 1.27%. A bigger bonus usually means a lower rate underneath, and that is exactly the pattern here: Plum has the largest bonus and the lowest standard rate. Some bonuses also come with conditions, such as a minimum balance or a limit on withdrawals, that can take the bonus away early.

Chip’s ISA rate is a tracker. Its standard rate sits a fixed margin below the Bank of England’s Bank Rate, currently 3.75%, so it moves when Bank Rate moves. Our guide to introductory bonus rates explains what to do when yours ends. Rates are variable. New-customer boosts last 12 months, then the standard rate applies.

Cash ISA apps compared

The table scrolls sideways on a phone. Chip is highlighted as our pick and is the only column we earn from.

Cash ISA apps compared: rates, bonuses, flexibility, minimums, withdrawals and who holds the money
Feature	ChipSmart Cash ISA	PlumCash ISA	MoneyboxCash ISA	Trading 212Cash ISA	MonzoCash ISA Pots
Headline rateWith boost length and the standard rate after	4.68% AER for 12 months, then 3.50% AER	4.73% AER variable for 12 months, then 2.54%	4.72% AER variable for 12 months, then 3.45%	3.6% AER variable, flexible, no boost	Fixed: 4.70% AER fixed for 1 year. Instant Access: 2.75% to 3.50% by plan
Size of the boost	1.18% AER for 12 months	Cash ISA bonus of 2.19% AER for the first 12 months	Cash ISA bonus of 1.27% AER for 12 months from opening	None	None; the fixed rate is fixed instead
Flexible ISA	Yes	Yes	Check the account terms	Yes	Instant Access: yes
Minimum	Check the app	From £1	£500 for the bonus rate	£1 deposit and withdrawal	Instant Access: no minimum
Withdrawal limits	Unlimited withdrawals; flexible, so you can put money back in the same tax year	The bonus may be lost after your fourth withdrawal or if the balance drops below £100	Cash ISA drops to the lower rate for the rest of the year after four or more withdrawals, or below £500	No withdrawal restrictions or penalties	Instant Access unlimited. Select Access: up to 3.65% with 2 or fewer withdrawals a year and £500 minimum
Who holds the money	A panel of UK banks including Barclays, Lloyds and HSBC	Citibank and Lloyds Bank	A panel incl. Nationwide, HSBC, Barclays, NatWest and others, max 50% at one bank	Not stated on the ISA terms page; see the money protection page	Monzo Bank Limited
Fee to hold it	None on the free plan	None on Basic	None for savings-only customers	No deposit or withdrawal fees	None; better Instant Access rates on paid plans
	Get £50Takes you to getchip.uk · Referral link

Chip Smart Cash ISA

Chip’s Smart Cash ISA pays 4.68% AER for 12 months, then 3.50% AER for new customers. It is a flexible ISA: you can withdraw and pay back in during the same tax year without using more of your allowance. Withdrawals are unlimited and there is no penalty. The ISA manager is Chip Financial Wealth Ltd, and the money is spread across a panel of UK banks including Barclays, Lloyds and HSBC.

Smart Cash ISA

Counts for £50

4.68%AER

for 12 months, then 3.50% AER

unlimited withdrawals; flexible, so you can put money back in the same tax year

Variable. Checked 16 October 2026. New-customer boosts last 12 months, then the standard rate applies.

Two details are worth knowing. First, transferring out or closing forfeits any unpaid interest, so if you plan to move it when the bonus ends, check when interest is paid. Second, the older Chip Cash ISA is closed to new customers; the Smart Cash ISA is the one open now. Our full guide to the Chip Smart Cash ISA covers transfers and how the rate is made up.

The Smart Cash ISA also counts towards Chip’s £50 referral bonus, paid on top of your interest if you qualify. You need to deposit £1,000 and hold it for 90 days in a row.

£50 in four steps

Current offer runs 1 October to 31 October 2026.

1Open our link on your phone, enter your email and download Chip within 30 days. Or type CHIP-XUD314 in the app within 14 days.
2Deposit £1,000 or more into the Smart Cash ISA, the Instant Access Account or the Prize Savings Account. You can split it between them.
3Keep at least £1,000 there for 90 days in a row. Dip below and the countdown starts again.
4The £50 is added to your Instant Access account once all the conditions are met.

Easy Access does not count. It pays more than Instant Access, but it is not on Chip’s eligible list. Neither is the Chip Pension.
New to Chip only. If you have ever held a Chip account, neither of us gets paid.
120 days in total. Everything, including the 90-day hold, has to be done within 120 days of being referred.

Join Chip with our linkTakes you to getchip.uk · Referral linkNot sure you qualify? Take the checker

Referral link: if you join Chip through our link or code and qualify, you and we each receive £50 from Chip. That is our only income and it does not change what we write. How we make money.

Plum Cash ISA

Plum’s Cash ISA has the highest headline rate here: 4.73% AER variable for 12 months, then 2.54%. It is flexible and opens from £1. The catch is underneath. The standard rate after the bonus is the lowest of these ISAs, and the bonus has strings attached: Plum’s FAQ says the bonus may be lost after your fourth withdrawal or if the balance drops below £100. If you transfer an existing ISA in, Plum quotes a transfer-in rate of 3.75%.

The Cash ISA money is held with Citibank and Lloyds Bank, protected by the FSCS per bank. See Plum’s Cash ISA page. Our Chip vs Plum comparison covers the apps more broadly.

Moneybox Cash ISAs

Moneybox has two Cash ISAs. The main one pays 4.72% AER variable for 12 months, then 3.45%, a standard rate very close to Chip’s 3.50% AER. It needs a balance of £500. Cash ISA drops to the lower rate for the rest of the year after four or more withdrawals, or below £500. That makes it a good home for money you will leave alone, and a poor one for anything you might dip into.

If you want easier access, the Open Access Cash ISA pays 3.80% AER variable incl. a 0.55% bonus for 12 months, from £1, unlimited withdrawals. Moneybox spreads ISA money across a panel incl. Nationwide, HSBC, Barclays, NatWest and others, max 50% at one bank. See Moneybox’s Cash ISA page and Open Access Cash ISA page, and our Chip vs Moneybox comparison.

Trading 212 Cash ISA

Trading 212’s Cash ISA pays 3.6% AER variable, flexible. There is no bonus, so nothing drops away after a year, and that rate is above Chip’s standard rate of 3.50% AER. Interest is earned daily, the minimum is £1, and there are no deposit or withdrawal fees.

Trading 212 is mainly an investing platform, and the app is built around that. Its interest on cash feature uses money market funds as well as banks, so read Trading 212’s money protection page and the Cash ISA terms to see where ISA cash sits. Our Chip vs Trading 212 Cash ISA comparison puts the two side by side.

Monzo Cash ISAs

Monzo is a bank, and its ISAs live as Pots inside the Monzo app, so you need a Monzo current account. There are three options:

Instant Access Cash ISA: 2.75% to 3.50% AER variable, by plan. 2.75% on the free plan, 3.50% on Max (from £19 a month). Flexible, unlimited withdrawals.
Fixed Rate Cash ISA Pot: 4.70% AER fixed for 1 year. The only fixed rate in this comparison.
Select Access ISA: up to 3.65% with 2 or fewer withdrawals a year and £500 minimum.

The fixed rate is the real draw. If you want to know exactly what you will earn and will not need the money for a year, it beats juggling boosts. See Monzo’s Cash ISA page and our Chip vs Monzo savings comparison.

Chase: no Cash ISA

Chase does not offer a Cash ISA. Its saver accounts and round-up account are taxable savings, so the interest counts towards your Personal Savings Allowance. If you bank with Chase and want an ISA, you will need another provider. See the Chase Saver page.

Flexibility and your allowance

You can pay up to £20,000 into ISAs this tax year, in one account or split across several. A flexible ISA lets you take money out and put it back before 5 April without that counting twice. With a non-flexible ISA, anything you withdraw is gone from your allowance for the year. Our flexible ISA guide explains the same-tax-year rule, and the Cash ISA allowance guide covers how the allowance splits across ISA types.

It is also worth checking whether you need an ISA at all. Under the Personal Savings Allowance, basic-rate taxpayers can earn £1,000 of interest a year tax-free and higher-rate taxpayers £500. If your interest will stay under that, the best easy-access rate may beat the best ISA rate. If you are a higher-rate taxpayer, or your savings are large, the ISA wrapper matters more.

Which one should you choose?

You want a simple, flexible ISA with a strong first year: Chip, and if you are new to Chip and keep £1,000 in for 90 days, the referral bonus too.
You want the best rate without a bonus cliff: Trading 212, once you are happy with how it holds your cash.
You want a fixed rate: Monzo’s Fixed Rate Cash ISA Pot.
You will not touch the money for a year: Moneybox’s main Cash ISA, with its higher standard rate than Plum.
You want the biggest number for 12 months and will move afterwards: Plum, as long as you can meet the bonus conditions.

For easy-access accounts as well as ISAs, see our full savings app comparison.

Join Chip and get £50 when you save £1,000 for 90 days

For the first 12 months, new customers get 3.51% AER (variable tracker) on Instant Access (then 3.00% AER) and 4.68% AER (variable tracker) on the Smart Cash ISA (then 3.50% AER). Use our link or the code CHIP-XUD314, deposit £1,000 into an eligible account and keep it there for 90 days.

Current offer runs 1 October to 31 October 2026. Had Chip before, or planning to use Easy Access? You will not get the bonus. Check in five questions.

Join on getchip.ukTakes you to getchip.uk · Referral link

Referral link: if you qualify, you and we each get £50 from Chip. Eligibility criteria apply. The £50 is for people who have never held a Chip account, who deposit £1,000 into an eligible account and keep at least £1,000 there for 90 days in a row. Rates are variable. New-customer boosts last 12 months, then the standard rate applies.

Frequently asked questions

Which app has the best Cash ISA rate?

On headline rate, Plum and Moneybox lead with 12-month bonuses, and Chip is close behind at 4.68% AER for 12 months, then 3.50% AER. Once the bonuses end, Trading 212’s 3.6% beats the standard rates of Chip, Moneybox and Plum, and Chip and Moneybox are close to each other. Monzo’s fixed Cash ISA Pot is the only fixed rate in this group.

What is a flexible Cash ISA?

A flexible ISA lets you take money out and put it back in the same tax year without using up more of your £20,000 allowance. Chip’s Smart Cash ISA, Plum’s Cash ISA and Trading 212’s Cash ISA are flexible. If you withdraw from a non-flexible ISA, that part of your allowance is gone for the year.

Can I have Cash ISAs with more than one app?

Yes. GOV.UK says you can split your £20,000 allowance across multiple accounts each tax year, as long as your total across all ISAs stays within it. That means you could take a boosted rate in one app and a fixed rate in another. Check each provider’s own terms before you split.

Does Chase have a Cash ISA?

No. Chase offers a saver account, a round-up account and a current account, but not a Cash ISA. If you want an ISA alongside a Chase account, you would need to open it with another provider. The Chase Saver’s boosted rate is not tax-free, so interest counts towards your Personal Savings Allowance.

What happens when a Cash ISA bonus ends?

The bonus falls away and you earn the standard rate. On Chip’s Smart Cash ISA that is 3.50% AER after 12 months. You can then stay, or transfer to another ISA. Use a proper ISA transfer rather than withdrawing, or the money loses its tax-free wrapper. With Chip, transferring out forfeits any interest not yet paid.

Does the Chip Smart Cash ISA count for the £50 referral bonus?

Yes. The Smart Cash ISA is one of the eligible accounts. You need to deposit £1,000 or more and keep at least that much there for 90 days in a row. If your balance dips, the countdown restarts. You must never have held a Chip account. The Easy Access Saver does not count.

Do I need a Cash ISA if I have the Personal Savings Allowance?

Maybe not. Basic-rate taxpayers can earn £1,000 of savings interest a year tax-free, and higher-rate taxpayers £500. If your interest stays under that, an ordinary savings account taxes the same as an ISA. An ISA still helps if your balance or rates grow, or if you pay tax at a higher rate.

Sources

Figures last checked 16 October 2026. If something has changed, tell us and we will correct it.