Cash ISA Guide UK

Cash ISA UK Tax-Free Savings With More Choice.

Understand how Cash ISAs work in the UK, how the ISA allowance applies, what to look for when comparing Cash ISA rates, and the difference between easy-access and fixed-rate options.

Explore Cash ISA Options → Explore Savings
✓ UK ISA guidance ✓ Tax-free interest explained ✓ 2026/27 rules
Person managing savings and considering a Cash ISA
Cash ISA interest Tax-Free Interest earned inside a Cash ISA is free from Income Tax.
£
2026/27 ISA allowance Overall annual ISA limit
£20,000
Cash ISA limit currently forms part of this overall allowance.
Eligibility 18+ You generally need to be 18 or over to open an ISA.
2026/27 £20,000 Overall annual ISA subscription limit.
Interest Tax-Free Interest earned within a Cash ISA is not subject to Income Tax.
From 2027 £12,000* Planned Cash ISA limit for under-65s from 6 April 2027.
What Is A Cash ISA?

A tax-efficient home for your cash savings

A Cash ISA is a type of Individual Savings Account that lets you earn interest on cash without paying Income Tax on that ISA interest.

Unlike a standard savings account, interest earned within an ISA does not need to be declared on your tax return. This can make Cash ISAs particularly relevant to savers who are earning enough interest to use some or all of their Personal Savings Allowance.

Cash ISAs can come with different access structures, including easy-access, notice and fixed-rate products. The best option depends on when you may need your money and how much flexibility you want.

Woman reviewing a Cash ISA savings plan
Cash savings planning
Cash ISA Types

Which type of Cash ISA could suit your savings?

Cash ISAs can differ significantly in how quickly you can access your money. Compare the structure before focusing on the interest rate alone.

01

Easy-Access Cash ISA

Designed for savers who want tax-free interest while retaining relatively easy access to their money.

  • Usually variable interest
  • Flexible access may be available
  • Useful for accessible savings
  • Check withdrawal limits
02

Fixed-Rate Cash ISA

A fixed-rate Cash ISA can offer a guaranteed interest rate for a set period, subject to the product's access conditions.

  • Fixed interest rate
  • Known return over the term
  • Access restrictions may apply
  • Check early-access charges
03

Notice Cash ISA

A notice Cash ISA requires advance notice before withdrawing money and can suit planned savings rather than emergency cash.

  • Notice period applies
  • Potentially competitive rates
  • Less immediate access
  • Plan withdrawals in advance
Person calculating annual ISA savings allowance
Cash ISA Allowance

How much can you put into a Cash ISA?

For the 2026/27 tax year, the overall ISA allowance is £20,000. You can use the allowance across eligible ISA types, subject to the individual limits that apply to products such as a Lifetime ISA.

You do not have to put the full £20,000 into a Cash ISA. You can split your annual ISA subscriptions between different types of ISA, provided you remain within the applicable rules.

£20,000 Overall ISA subscription limit for the 2026/27 tax year.
The tax year runs from 6 April to 5 April.
Important 2027 Change

Cash ISA rules are scheduled to change from April 2027

The government has announced reforms to the Cash ISA allowance. Understanding the planned change matters if you are building a long-term savings strategy.

2026/27

Current Cash ISA position

For the 2026/27 tax year, the overall ISA allowance is £20,000 and the current Cash ISA rules remain in place.

  • Overall ISA allowance: £20,000
  • Cash ISA interest remains tax-free
  • Multiple ISA types can be used
  • Transfer rules continue to apply
From 6 April 2027

New Cash ISA limit for under-65s

The planned reform will reduce the Cash ISA subscription limit to £12,000 for people under 65 while keeping the overall ISA allowance at £20,000.

  • Cash ISA limit: £12,000 for under-65s
  • Overall ISA limit remains £20,000
  • Cash ISA limit remains £20,000 for age 65+
  • Additional transfer restrictions are planned
Important: The 2027 Cash ISA reforms are scheduled for 6 April 2027. Always check the latest HMRC and GOV.UK guidance before acting because legislation and implementation details can change.
Cash ISA Rates

Don't compare Cash ISA rates in isolation

Cash ISA interest rates can vary between providers and products. A headline rate may depend on conditions such as a new-customer bonus, transfer eligibility, minimum deposits or a fixed term.

When comparing the best Cash ISA rates, look at the full account structure alongside the AER.

%
AER Compare the annual equivalent rate.
Compare
£
Minimum deposit Check how much you need to open the account.
Check
↔
Withdrawals Understand access restrictions and charges.
Review
★
Bonuses Check how long promotional rates actually last.
Check
Woman comparing Cash ISA interest rates
Person transferring money between savings accounts
Cash ISA Transfers

Moving your Cash ISA? Use the proper transfer process

If you find a better Cash ISA rate, you can usually transfer your ISA savings to another provider. To preserve the tax-free ISA status, the transfer should be arranged through the ISA providers rather than withdrawing the money yourself.

Providers can have different transfer processes, and some may charge for transferring certain fixed-rate products.

01
Compare the new account Check the rate, access conditions and whether the provider accepts ISA transfers.
02
Ask the new provider to transfer Complete the provider's ISA transfer process so the tax-free status is maintained.
03
Check charges and restrictions Fixed products may have early-access or transfer consequences.
04
Confirm completion Check that the new provider has received and processed the transfer correctly.
Tax Benefits

Why is Cash ISA interest tax-free?

Interest earned inside a Cash ISA is not subject to Income Tax. This is one of the main reasons savers consider ISAs when comparing them with ordinary taxable savings accounts.

The Personal Savings Allowance applies to ordinary savings interest, but ISA interest is treated differently and remains outside the normal taxable savings-interest calculation.

No Income Tax on ISA interest Interest earned within a Cash ISA is tax-free.
No ISA interest declaration ISA interest does not need to be declared on your tax return.
Useful for higher savers Tax-free interest can become more valuable as taxable savings interest increases.
Rules still matter Always check the current ISA allowance and transfer rules.
Before Opening A Cash ISA

Use this checklist before choosing a Cash ISA

A higher Cash ISA rate is not automatically the best option. Consider access, transfer rules, bonuses and your own savings timeline.

✓ Compare the current AER rather than the headline rate alone.
✓ Check whether the rate is variable or fixed.
✓ Understand withdrawal limits and early-access charges.
✓ Check whether the account accepts ISA transfers.
✓ Look for introductory bonuses and their expiry dates.
✓ Check minimum deposits and maximum balance limits.
✓ Check whether the ISA is flexible.
✓ Consider the planned 2027 Cash ISA allowance changes.
Person checking Cash ISA account details
Explore More

Related savings guides

Compare Cash ISAs with other UK savings options and understand how access, rates and account structures differ.

Savings · 01

Easy Access Savings

Learn how flexible savings accounts work and when instant access can be more important than a higher rate.

Explore Easy Access → Savings · 02

Fixed Rate Savings

Understand fixed-term savings and how guaranteed rates compare with flexible savings options.

Explore Fixed Savings → Savings · 03

Notice Savings Accounts

Learn about notice periods, planned withdrawals and savings accounts that sit between easy access and fixed terms.

Explore Notice Savings → Savings · 04

Regular Savings Accounts

Explore regular saver accounts, monthly deposits and interest rate conditions.

Explore Regular Savings → Savings · 05

Children's Savings

Understand children's savings accounts, Junior ISAs and long-term saving options.

Explore Children's Savings → Savings · 06

UK Savings Guides

Explore the complete GrowthSmartly collection of UK savings account guides.

View All Savings →
Frequently asked questions about Cash ISAs
Frequently Asked Questions

Cash ISA questions answered

Straightforward answers to common questions about Cash ISA allowances, rates, withdrawals, transfers and tax-free interest.

A Cash ISA is an Individual Savings Account that holds cash and pays interest without Income Tax being charged on that ISA interest.
The overall ISA subscription limit for 2026/27 is £20,000. This allowance can be used across eligible ISA types, subject to the relevant product rules.
Yes. Interest earned within a Cash ISA is free from Income Tax under the ISA rules.
Current rules allow you to pay into more than one Cash ISA in a tax year, provided you stay within the overall ISA subscription limits and follow the provider's rules.
You can generally withdraw money from an ISA, although your provider may have account-specific rules or charges. If the ISA is flexible, you may be able to withdraw and replace money within the same tax year without reducing that year's allowance.
A flexible Cash ISA allows you to withdraw money and replace it during the same tax year without reducing your current-year ISA allowance, subject to the provider offering the flexible feature.
Yes. You can generally transfer an existing ISA to another provider. Use the provider's ISA transfer process rather than withdrawing the money yourself if you want to preserve its ISA tax benefits.
From 6 April 2027, the planned Cash ISA subscription limit will be £12,000 for people under 65. The overall ISA allowance will remain £20,000, while people aged 65 and over will retain a £20,000 Cash ISA limit.
It depends on your circumstances. A Cash ISA provides tax-free interest, while a standard savings account may offer different rates, access or features. Your tax position and savings goals should be considered when comparing them.
Eligible deposits held with an authorised UK bank, building society or credit union may be protected by the Financial Services Compensation Scheme, subject to the applicable rules and limits. Check the provider's protection status before depositing significant amounts.
Smarter Savings

Make your savings work harder, tax-free.

Compare Cash ISA structures, understand the allowance and explore different savings options before deciding where your money fits.

Explore Savings → Easy Access Savings Fixed Rate Savings
Important: GrowthSmartly provides general financial education and information. It does not provide personalised financial, investment, tax or legal advice. Cash ISA rates, allowances, provider conditions, tax rules and ISA legislation can change. The 2027 Cash ISA reforms referenced on this page are based on current government announcements and should be checked against the latest GOV.UK guidance before making a financial decision.
Scroll to Top