ISA Deadline 5 April 2027: End-of-Year Checklist (Act Before the Tax Year Closes)

Every tax year, millions of pounds in ISA allowance simply vanishes at midnight on 5 April. There is no grace period, no rollover, no way to claim back unused allowance in the following year. If you have £20,000 sitting in a current account earning little or no interest, the cost of not moving it into an ISA before the deadline is measured in tax-free interest or growth you can never recover.

For the 2026/27 tax year, the deadline is 5 April 2027. The allowance resets on 6 April 2027 — but the 2026/27 allowance, unused, is gone forever. This checklist tells you exactly what to do, in what order, and by when.

Why the Deadline Matters: Use-It-or-Lose-It Explained

An ISA allowance is the maximum you can contribute to ISAs in a single tax year. In 2026/27:

• Cash ISA + Stocks and Shares ISA + Innovative Finance ISA: £20,000 combined
• Lifetime ISA: up to £4,000 of the £20,000 (counts towards, not in addition to, the £20,000)
• Junior ISA (JISA): £9,000 per child (separate from the adult £20,000)

The key rule: unused allowance from one tax year cannot be carried forward. If you contribute £12,000 in 2026/27, your remaining £8,000 of 2026/27 allowance disappears at midnight on 5 April 2027. You cannot add it to next year's £20,000. You cannot claim it back later. It is gone.

This is categorically different from pension annual allowance, where unused allowance can be carried forward for up to three years.

The consequence: even a modest 4–5% AER cash ISA rate means £8,000 of unused allowance costs you roughly £320–£400 per year in taxable interest you could have earned tax-free. And for Stocks and Shares ISA investors, gains on £8,000 left outside the wrapper are subject to capital gains tax once you exceed the CGT annual exemption.

The LISA Bonus: Act by 5 April

The Lifetime ISA (LISA) pays a 25% government bonus on contributions up to £4,000 per tax year — a maximum bonus of £1,000 per year. The bonus is paid on contributions made within the tax year; contributions made after 5 April are credited to the next year's allowance.

If you are between 18 and 39 and opening a LISA for a first home or retirement, the bonus is free money — worth chasing even if you have limited funds. A £4,000 contribution by 5 April 2027 receives a £1,000 bonus, credited within 6–8 weeks of the end of the tax year.

Note: the LISA withdrawal penalty — currently 25% of the amount withdrawn — effectively claws back the bonus plus a small additional amount (approximately 6.25% of your own contributions). Only use a LISA if you are genuinely buying a first home under £450,000 or saving for retirement from age 60.

JISA: £9,000 Per Child, Per Year

The Junior ISA allowance is £9,000 per child per tax year. It is a separate allowance — it does not reduce your £20,000 adult allowance. Like the adult ISA, it is use-it-or-lose-it.

JISAs can be cash or Stocks and Shares. For children with 10+ years until they can access the funds (age 18), a Stocks and Shares JISA typically outperforms cash over the long term, though it carries market risk.

Parents and guardians can open a JISA; any person can contribute to it (up to the annual limit).

ISA Types and How to Split the £20,000

The £20,000 can be split across different ISA types in any combination, with one restriction per type:

You can hold a cash ISA and a Stocks and Shares ISA simultaneously and split contributions between them within the £20,000. Since April 2024, you can also open multiple ISAs of the same type with different providers in the same tax year (a previous restriction was removed).

Platform Comparison: Rates and ISA Terms (2026)

Rates and terms change frequently. These figures were indicative in mid-2026 and should be verified directly with providers before opening an account.

For long-term wealth building, even a 0.5% rate difference compounds significantly. Use our compound interest calculator to see how a 4.5% vs 5.1% AER on £20,000 over 10 years diverges — it is a larger gap than most people expect.

The Transfer Timing Problem

If you want to move money between ISA providers before the tax year end, timing is critical. As covered in detail in our ISA transfer guide:

• Cash ISA transfers must complete within 15 business days under FCA rules
• Stocks and Shares ISA transfers take 30–60 days (cash) or longer (in-specie)

Practical implication: if you want your ISA transfer to definitely be in place before 5 April 2027, initiate it by:

• Cash ISA: no later than 12 March 2027 (15 business days before 5 April, allowing buffer)
• Stocks and Shares ISA: no later than 20 February 2027 (to allow 30+ days)

Do not initiate a transfer in the last week of March and assume it will complete in time. If it does not, your money may sit between providers in limbo over the tax year end — this does not affect your existing ISA allowance (the money is still within the wrapper), but you cannot add new money to an account that is mid-transfer.

Crucially, never withdraw from your ISA to re-deposit elsewhere. This destroys the allowance permanently. Always use the formal ISA transfer process.

Approaching £100,000? Consider Your SIPP Instead

If you have already used or plan to use the full £20,000 ISA allowance and have surplus savings, the next most tax-efficient vehicle is typically a Self-Invested Personal Pension (SIPP).

The pension annual allowance for 2026/27 is £60,000 (or 100% of relevant earnings, whichever is lower). Contributions receive income tax relief at your marginal rate:

• Basic rate taxpayer: contribute £800, pension receives £1,000 (20% relief added)
• Higher rate taxpayer: contribute £600, pension receives £1,000 (40% relief claimed via self-assessment)

ISA money grows tax-free on withdrawals; pension money is taxed on withdrawal (except the 25% tax-free lump sum). For most people, both are beneficial and the choice between them depends on your marginal rate now vs expected rate in retirement.

At or approaching £100,000 salary, the personal allowance taper creates a 60% effective marginal rate on income between £100,000 and £125,140. Pension contributions in this range deliver 60% effective tax relief — the strongest savings incentive available to UK individuals.

5 Common ISA Mistakes to Avoid

1. Closing your ISA account instead of transferring. Closing or withdrawing creates a permanent loss of that portion of your allowance (unless you have a Flexible ISA).

2. Opening a new ISA and depositing fresh money rather than initiating a transfer. If you withdraw from provider A and deposit to provider B, you have used double the allowance — once when you deposited at A, and again when you re-deposit at B (both count against your annual limit).

3. Assuming you can split £20,000 with a new subscription to a fixed-rate ISA mid-year. Many fixed-rate cash ISAs do not accept partial contributions after opening. If you open a 1-year fixed ISA at £10,000 and want to add the remaining £10,000 in March, check whether the product allows this.

4. Missing the LISA contribution deadline. The LISA bonus is calculated on contributions received within the tax year. A contribution that clears on 6 April (the day after the deadline) misses the current year's bonus.

5. Subscribing to the same ISA type twice with different providers. Pre-April 2024 rules required you to subscribe to only one ISA of each type per year. Since April 2024 this restriction was lifted, but not all providers have updated their documentation to reflect this. Check your provider's terms if you want to open a second cash ISA.

5-Step End-of-Year Checklist

Work through this in order, starting no later than March 2027:

Step 1: Know your used allowance. Log in to each ISA you hold and total up all contributions made since 6 April 2026. Ensure the total does not exceed £20,000. Include any LISA contributions in this total.

Step 2: Decide how much you can contribute before 5 April 2027. Check your current account, savings accounts, and investment accounts for surplus cash. Amounts you can afford to lock away (S&S ISA or fixed-rate cash ISA) vs. amounts you need easy access to (easy access cash ISA) should be directed to appropriate products.

Step 3: Initiate any transfers by early March at the latest. If you want to move ISA money to a better-rate provider, start the transfer by 12 March 2027 (cash ISA) or earlier (S&S ISA). Remember: never withdraw — always transfer via the receiving provider's form.

Step 4: Top up your LISA if eligible. If you are 18–39, have a LISA for a first home or retirement, and have not yet contributed £4,000 in 2026/27, add funds to capture the £1,000 bonus. Do this by 31 March at the latest to ensure funds clear by 5 April.

Step 5: Make your final contributions. Transfer funds into your ISA(s) before midnight on 5 April 2027. Online bank transfers are generally instant or next-day. Direct debits or cheques need more lead time — aim for 2 April at the latest if using these methods.

Key Takeaways

• The 2026/27 ISA allowance is £20,000; any unused portion disappears permanently at midnight on 5 April 2027.
• The LISA bonus of up to £1,000 per year is only paid on contributions made within the tax year — contribute by 5 April.
• ISA transfers must be initiated weeks before the deadline (12 March for cash ISA; February for S&S ISA) to ensure they complete in time.
• Never withdraw and re-deposit — always use the formal ISA transfer process via the receiving provider.
• If you have already maximised your ISA allowance and earn over £100,000, pension contributions in the 60% effective tax relief zone deliver the most powerful savings incentive available.