Best Cash ISA Apps in the UK Compared

Picking the best cash ISA app UK savers can open in 2026 used to be a simple hunt for the biggest number. It is not any more, for two reasons. The headline rate on most app ISAs is now a moving target that resets when the Bank of England moves or when a twelve month bonus falls away, and the rules governing how much you can shelter in cash are about to change for the first time in years. Both of those matter more to your actual return than a tenth of a percent on the day you sign up.

This guide compares the main app-based cash ISAs on the things that do not change every fortnight: how the rate is constructed, whether the account is flexible, what happens if you withdraw, and which bank is really holding your money.

The rule change you should plan around first

From 6 April 2027, the amount an under-65 can pay into a cash ISA in a single tax year drops from £20,000 to £12,000. The overall ISA allowance stays at £20,000; the balance has to go into a stocks and shares, Lifetime or Innovative Finance ISA instead. Savers aged 65 and over keep the full £20,000 cash limit.

That makes 2026/27 the last tax year in which most people can shelter a full £20,000 in cash. If you have a large sum sitting in a taxable easy-access account, the sensible move is to use this year’s cash allowance properly rather than dripping it in. HMRC has also published anti-circumvention rules to stop people gaming the transition, so do not expect a clever workaround to survive.

How app cash ISA rates are actually built

Three different structures dominate, and they suit different savers.

Base rate trackers. Trading 212’s cash ISA is pegged to the Bank of England base rate minus a fixed margin. The advantage is honesty: you always know where the rate came from and it will never quietly rot while you ignore it. The disadvantage is that it falls the moment the Bank cuts, with no notice period.

Bonus rates. Moneybox has long used an introductory rate for the first twelve months that steps down to a lower ongoing rate afterwards. These accounts win comparison tables on day one and lose them on day 366. They are fine if you diarise the drop and move, and quietly expensive if you do not.

Standing variable rates with strings. Plum’s highest-paying cash ISA tier restricts you to a small number of withdrawals per year, and Chip has generally run a straight variable easy-access rate with no introductory bonus. A restricted-withdrawal account can be the right answer for money you genuinely will not touch, and the wrong answer for an emergency fund.

If you cannot say which of those three your account is, you do not know what you own. Check before you deposit, not a year later.

Flexible versus non-flexible: the detail most people miss

A flexible cash ISA lets you withdraw money and replace it in the same tax year without the replacement eating into your allowance. A non-flexible one does not: take out £5,000 and put it back, and you have used £5,000 more of your £20,000.

Trading 212’s cash ISA is flexible with no cap on withdrawals, which is unusual and genuinely useful. Several app ISAs are not flexible at all. This matters enormously if the account is doubling as your emergency fund, and not at all if you are parking a house deposit you will not touch. It is the single question worth asking before the rate.

Who is actually holding your money

App providers are rarely banks. Most are e-money or investment firms that place your deposit with one or more partner banks, and your Financial Services Compensation Scheme protection sits with those banks, not with the app. Two consequences follow.

First, the £85,000 FSCS limit applies per banking licence, so if the partner bank behind your app ISA is the same institution where you already hold savings, your two balances are added together for protection purposes. Second, some apps spread deposits across several partners, which changes the picture again.

Every provider is required to name its partner banks. Find that page before you deposit. We cover the mechanics in more detail in our guide to whether savings apps are safe and in the Plum FSCS explainer.

Which app suits which saver

• You want set-and-forget with no rate rot: a base rate tracker like Trading 212, especially given it is flexible.
• You want the highest number and will actually move in twelve months: a bonus-rate account such as Moneybox, with a calendar reminder.
• You want everything in one place: Moneybox is the only one of these offering cash ISA, stocks and shares ISA, Lifetime ISA, Junior ISA and a pension under one login, which is worth something if you value not juggling four apps.
• You want automated saving on top of the ISA: Plum and Chip both bolt round-ups and automated transfers onto the savings side, covered in our round-up savings apps comparison.
• You are saving an emergency fund: prioritise flexibility and unlimited withdrawals over the headline rate. A restricted-withdrawal tier is the wrong tool.

Transferring an existing cash ISA in

Never withdraw money from an old ISA to move it. Use the receiving provider’s transfer form, which preserves the tax-free wrapper on everything you have built up in previous years. Most app providers now handle cash ISA transfers in-app, and current-year subscriptions must be transferred in full while previous years can be moved in part.

Transfers of cash ISAs are supposed to complete within 15 working days. If yours stalls beyond that, chase the receiving provider, since they are the ones driving the process.

Frequently asked questions

What is the best cash ISA app in the UK right now? There is no permanent winner, because rates reset constantly. On structure rather than headline rate, Trading 212 is the strongest option for savers who want a flexible, base-rate-tracking account they never have to babysit, and Moneybox suits people who want the whole ISA family in one app and will move when the introductory rate ends.

Is a cash ISA still worth it if I pay basic rate tax? Often yes, and increasingly so. The personal savings allowance covers £1,000 of interest for basic rate taxpayers and £500 for higher rate, but a moderate balance at current rates can exceed that. Additional rate taxpayers get no allowance at all, so an ISA is doing real work from the first pound.

How much can I put in a cash ISA in 2026/27? Up to £20,000, which is the full ISA allowance, provided you are not also subscribing to other ISA types in the same year. From 6 April 2027 that cash figure falls to £12,000 for savers under 65.

Are app cash ISAs covered by the FSCS? The deposits are, but the protection sits with the partner bank holding the money rather than the app itself. Check which bank that is, because balances at the same banking licence share a single £85,000 limit.

Can I have more than one cash ISA? Yes. Since April 2024 you can pay into multiple ISAs of the same type in one tax year, as long as you stay within the overall allowance. That makes it much easier to open a better-paying account mid-year without moving the old one.

Does withdrawing from a cash ISA lose my allowance? Only if the account is non-flexible. In a flexible cash ISA you can replace withdrawn money in the same tax year with no cost to your allowance. In a non-flexible one, the replacement counts as a fresh subscription.