Tax-Year-End ISA Checklist
Last updated: · PlainISA
Why 5 April matters
The UK tax year runs from 6 April to 5 April. Every ISA subscription made before 5 April midnight counts against the closing tax year's £20,000 allowance. Unused allowance does NOT roll over, it is permanently lost at the boundary. A saver who subscribes only £8,000 of their £20,000 capacity by 5 April loses access to the remaining £12,000 forever.
This makes the 1-5 April window the most consequential five days of the financial year for many UK savers. Decisions deferred past 5 April cannot be undone retroactively.
The checklist
1. Verify how much allowance you have left
Add up all ISA subscriptions you have made across providers since 6 April of the current tax year. Include Cash ISA + S&S ISA + LISA + IFISA. Subtract from £20,000 to find your unused capacity. For LISA specifically, the sub-limit is £4,000, track this separately.
If you have flexible ISAs and have made replacement deposits during the year, those re-deposits do NOT count against your subscription allowance. Only "new" net contributions count.
2. Decide whether to top up
The 25% LISA bonus is the highest-priority top-up if you are eligible (18-39 at opening, 18-50 for ongoing subscriptions, with first-home or retirement goal). Each £1 subscribed before 5 April attracts £0.25 of HMRC bonus credited within 4-9 weeks. Maximising the £4,000 LISA cap before tax-year-end captures £1,000 of guaranteed return.
For Cash ISA top-ups, even £100 of additional subscription generates compounding interest for the full following year. If you have unused allowance and surplus cash earning 0% in a current account, moving it into a Cash ISA is virtually a free trade.
3. Initiate any transfers IN PROGRESS
If you intend to transfer an ISA from one provider to another, initiate the transfer at least 21 calendar days before 5 April. Cash ISA transfers should complete within 15 business days but holiday periods and provider backlogs can stretch this. S&S ISA transfers routinely take 4-6 weeks. A transfer that doesn't complete by 5 April is not a problem for the prior-year balance, but if the transfer involves current-year subscriptions, an incomplete transfer at 5 April can lock you out of further subscriptions at the destination until completion.
4. Plan provider concentration risk
FSCS protection is £85,000 per banking licence (Cash ISA) or £85,000 per fund manager (S&S ISA). If your total Cash ISA balance approaches £85,000 at a single provider, consider splitting subscriptions for the new tax year across a second provider to keep the entire balance within protection.
5. Review S&S ISA holdings for tax-loss harvesting
Capital gains inside an ISA are exempt, but losses inside an ISA are NOT usable to offset gains outside an ISA. If you are sitting on substantial unrealised losses in a taxable General Investment Account and corresponding gains inside an ISA, consider whether selling the GIA losses before 5 April (and re-buying after the 30-day "bed-and-breakfast" window) creates a useful loss to carry forward. This is a personal tax strategy outside ISA mechanics but interacts with year-end planning.
6. Junior ISA top-ups
If you have children under 18, the Junior ISA annual allowance is £9,000 per child per tax year. This is fully separate from the adult £20,000, topping up the Junior ISA does not consume the parent's allowance. Decisions to top up Junior ISA must also be made before 5 April; unused allowance is lost.
7. Open accounts in advance
Opening a brand-new ISA account at a new provider can take 2-5 business days for KYC checks (proof of identity, proof of address, account opening). If you intend to use 5 April to subscribe to a new provider, open the account no later than 1 April. The £20,000 allowance can be subscribed in a single lump sum on 5 April, but the account must be live and able to accept the deposit.
8. Confirm pension contributions are separate
The £20,000 ISA allowance is entirely separate from the £60,000 pension annual allowance (or your reduced allowance if you are subject to the tapered annual allowance). Top up both wrappers if you have capacity. The pension annual allowance has a separate 5 April deadline and additionally allows 3-year carry-forward of unused capacity, which the ISA does not.
What to AVOID at year-end
- Don't close an ISA to "free up cash" if you intend to re-open later. Closure voids the tax-free status of the entire balance. Use the transfer process or the flexible-ISA replace mechanism instead.
- Don't over-subscribe across providers. HMRC reconciles across all providers; the £20,000 cap is total, not per-provider. Over-subscription triggers HMRC voiding the excess.
- Don't subscribe to a LISA at age 39 days-before-40 expecting to use it in your 40s. The wrapper can be subscribed only until age 50, and the saver must be aged 18-39 at the time of OPENING. Opening last-minute means you have a working window but must understand the structure.
A quick yes/no decision tree
- Have I subscribed less than £20,000 across all my ISAs this tax year? → Top up if cash is available.
- Am I aged 18-39 and have not yet opened a LISA? → Strongly consider opening one before age 40 to lock in lifetime bonus eligibility.
- Have I subscribed less than £4,000 to my LISA this year? → Top up for the 25% bonus.
- Are any of my children's Junior ISAs unused for the year? → Top up.
- Do I have an ISA transfer pending? → Confirm it has completed; chase the provider if not.
Sources
- gov.uk, Individual Savings Accounts
- gov.uk, Junior ISA
- gov.uk, Personal Savings Allowance + interest taxation
Quick reference table
| ISA type | Allowance | Age |
|---|---|---|
| Cash | £20,000 | 16+ |
| Stocks & Shares | £20,000 | 18+ |
| Lifetime | £4,000 | 18-39 |
| Junior | £9,000 | 0-17 |
Key takeaways
Editorial perspective
The right ISA wrapper depends on time horizon, age, and goal, not on which one has the highest headline return. Provider-neutral framework guidance lets savers make informed decisions without product-steering. - PlainISARelated guides
- ISA Types Explained: Cash, S&S, LISA, IFISA - compare all four wrapper types side-by-side.
- The £20,000 Annual Allowance and Rules - how the cap works and the 2024 multiple-ISA rule.
- Transferring an ISA - preserve tax-free status when moving providers.
- Flexible ISA Explained - withdraw and replace within the tax year.
- Lifetime ISA Bonus Mechanics - the 25% HMRC top-up + early-withdrawal arithmetic.
- Tax-Year-End Checklist - pre-5-April actions to maximise the allowance.
- Which ISA for My Goal? - wrapper choice by saver goal.
Editorial note
PlainISA covers UK Individual Savings Account rules with a focus on plain-language explanation, source-cited mechanics, and goal-oriented decision framing.
We are not a financial adviser. The content here is informational only, for personalised advice, consult an FCA-authorised adviser.
Last reviewed by PlainISA against the HMRC ISA Manual and the gov.uk Individual Savings Accounts page on the date stamped at the top of this guide.
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