Fixed vs Easy-Access Cash ISA (2026): Should You Lock In Before Rates Fall Again?

For most people the answer isn't one or the other — it's both, split by when you'll need the money. As of 18 August 2026, the best easy-access cash ISA paid 4.56% AER and the best one-year fix paid 4.7% AER (MoneySavingExpert). That's a difference of about 0.14 percentage points, or roughly £14 a year on £10,000. It's not much to give up instant access for.

A cash ISA is a savings account where the interest is free of UK income tax. AER means Annual Equivalent Rate — the rate you'd earn over a year with interest compounding, which is what makes accounts comparable.

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TL;DR

• Best easy-access ISA: 4.56% AER (Trading 212), including a 0.96% bonus for 12 months on new money, as of 18 August 2026 (MoneySavingExpert).
• Best fixed ISAs: 4.7% AER one-year, 4.77% two-year, 4.8% three-year, 4.85% five-year, as of 18 August 2026 (MoneySavingExpert).
• The gap is small. About 0.14 points between the best one-year fix and the best easy-access deal, and only 0.15 points between the best one-year and five-year fixes.
• Bank Rate is 3.75%, held for the fifth time in 2026 on 30 July, with three of nine MPC members voting to raise it (Fortune, 30 July 2026).
• The real decision is when you need the money, not what rates might do.

The honest comparison

The case for easy-access: you keep control. If rates rise, you benefit. If you need the money for a boiler or a job gap, it's there. And right now the rate penalty for that flexibility is genuinely tiny.

The case for fixing: certainty. Variable rates can be cut with a month's notice; a fix can't. If Bank Rate does fall from 3.75%, easy-access ISA rates will follow it down within weeks, and a fix protects you from that.

The case against long fixes: as MoneySavingExpert notes, there's little difference in rate between the top shorter and longer fixes. Locking money for five years to earn 0.15 points more than a one-year fix means giving up four extra years of flexibility for almost nothing.

The bonus trap on easy-access rates

This is the single most important thing to understand about headline easy-access rates: most of them are temporary.

Look at the current top of the table as of 18 August 2026:

• Trading 212, 4.56% AER — includes a 0.96% bonus for 12 months, on new money only.
• Chip, 4.55% AER — includes a 0.8% bonus for 12 months on new and transferred money.
• Plum, 4.36% AER — includes a 1.82% bonus for the first year.
• Charter Savings Bank, 4.23% AER — no bonus.

The Plum example makes the point starkly: strip the bonus and the underlying rate is around 2.54%. Trading 212 is more transparent than most — its help centre says the standard rate is set 0.15 percentage points below Bank Rate, which works out at 3.60% with Bank Rate at 3.75%. So its 4.56% is 3.60% plus the 0.96% bonus.

None of this makes bonus accounts bad. A year at 4.56% is a year at 4.56%. It makes them accounts you have to actively manage. Put the bonus end date in your calendar the day you open the account, and plan to move.

If you'd rather not play that game, Lightyear's cash ISA takes the opposite approach — it's designed to closely track Bank Rate, paying 3.75% AER with no bonus, no minimum deposit and full flexibility (Good Money Guide, February 2026). Lower headline rate, no cliff edge, nothing to diarise. That's a legitimate trade if you know you won't chase rates.

How to decide: three questions

1. When might you need this money?

• Within 12 months, or you're not sure: easy-access. The 0.14-point premium on a one-year fix isn't worth an early-withdrawal penalty that can cost several months' interest.
• Definitely not for 1–2 years: a one- or two-year fix is reasonable.
• Definitely not for 5 years: ask yourself whether this should be cash at all. Over five years, money you don't need has historically done better invested — though it can also fall in value, which cash won't.

2. Will you actually move when the bonus ends?

Be honest. If the answer is "probably not", the effective rate on a bonus account is closer to its underlying rate. A fix or a base-rate tracker may beat it in practice, even if it looks worse on the comparison table.

3. How much is at stake?

On £2,000, the difference between 4.56% and 4.7% is under £3 a year. Not worth thinking about. On £20,000 it's about £28 — still small next to the cost of getting the access decision wrong.

The split that works for most people

Three to six months of essential spending in an easy-access cash ISA. Everything beyond that, allocated by when you need it.

• Emergency fund: easy-access, always. Its job is to be available, not to maximise return.
• Money for a known expense 12–24 months out — a wedding, a car, a deposit top-up: a fix matching that timeline.
• Money with no purpose and no timeline: this is the pile worth thinking about properly. Cash ISA rates above 4% are good, but they're not a long-term growth strategy. Our stocks and shares ISA for beginners guide covers the alternative honestly, including the risks.

What April 2027 means for the money you fix today

The ISA rules change on 6 April 2027, and it affects fixes maturing around then.

From that date, under-65s can pay a maximum of £12,000 a year into cash ISAs, down from £20,000. The overall ISA allowance stays at £20,000 (GOV.UK).

The good news: a maturing cash ISA transferred into another cash ISA is a transfer, not a new subscription — so it doesn't touch your £12,000 (GOV.UK, transferring your ISA). Your existing balance stays sheltered. Providers must complete cash ISA transfers within 15 working days.

The thing to watch: if your fix matures and you take the money out instead of transferring it, putting it back into a cash ISA in 2027/28 would count against the reduced £12,000 limit. Always transfer, never withdraw and re-deposit.

The other change: from 6 April 2027, under-65s can't transfer money from a stocks and shares ISA into a cash ISA at all. That's a one-way door, and we've explained it fully in the ISA one-way door.

How to open or move a cash ISA

1. Check your remaining allowance. £20,000 across all ISAs in 2026/27, including anything you've paid into a stocks and shares ISA.
2. Check who actually holds your money. FSCS protection for cash deposits is £120,000 per person, per firm — but it's per banking licence. Some app-based providers use partner banks, so if you already save with that bank, your protection is shared.
3. Open the new account first if you're moving an existing ISA.
4. Use the transfer form, never a withdrawal. Withdrawing means that part of your allowance is gone for good unless the ISA is flexible.
5. For easy-access accounts, diarise the bonus end date immediately.
6. For fixes, note the maturity date and what happens by default — some providers roll you into a new fix automatically at a much worse rate if you don't instruct them.

If you want the current rate table rather than the decision framework, our best cash ISA rates roundup tracks the top deals, and we've reviewed the market-leading easy-access account in detail in our Trading 212 cash ISA review.

The bottom line

Fix money you're certain about, keep the rest accessible, and don't try to time Bank Rate. With the best fix paying only about 0.14 points more than the best easy-access account as of 18 August 2026, the flexibility is nearly free — take it unless you have a specific reason not to. And whichever you choose, the biggest single thing you can do for your return is to notice when your bonus ends.

This is general information, not financial advice. Rates are as reported on 18 August 2026 and move frequently — always check the live rate and terms with the provider before applying. FSCS protection depends on the authorised firm holding your deposit. Do your own research and consider speaking to a qualified adviser for your situation.

Last updated: 20 August 2026.