Photo by Kelly Sikkema on Unsplash

End of Tax Year Checklist UK 2026: What to Do Before 5 April

The end of tax year checklist UK 2026 matters more right now than at any other point on the financial calendar. With 5 April just days away, you have a rapidly closing window to use allowances that are, without exception, gone forever once the clock strikes midnight.

This is not a drill. Every year, millions of UK adults let their £20,000 ISA allowance lapse, forget to top up their pension, and miss out on free tax relief they were entitled to claim. These are not small stakes. A couple who both let their ISA allowance lapse for five years in a row have quietly left £200,000 of tax-protected investment space on the table — space they can never recover.

This guide gives you a clear, prioritised checklist. If you only have 30 minutes, do item one. If you have a couple of hours this week, work through all five. By 11:59pm on 5 April 2026, you want to close this page knowing you have left nothing on the table.

Let's start with why the deadline is so absolute.

Why 5 April Is the Most Important Date in Your Financial Calendar

The UK tax year runs from 6 April to 5 April the following year. It has done so since 1752, when Britain switched from the Julian to the Gregorian calendar and the Treasury refused to lose 11 days of tax revenue. The exact date is, in other words, an accident of history — but the consequences of missing it are entirely real.

Every single allowance discussed in this article operates on a use-it-or-lose-it basis. There is no carrying your ISA allowance forward to next year. There is no backdating a contribution to avoid this year's tax. When 5 April passes, the 2025/26 tax year is sealed, and a brand new set of allowances opens on 6 April 2026 — none of which can retrospectively cover anything you failed to do before the deadline.

The amounts involved are significant. Every adult in the UK gets a £20,000 ISA allowance each year. Every pension saver benefits from tax relief on contributions. Every investor has a £3,000 capital gains tax exemption. Couples can transfer unused personal allowances. Parents can shelter up to £9,000 per child in a Junior ISA.

None of this requires you to be wealthy. A £50-a-month cash ISA contribution by someone on an average UK salary of £35,000 still builds meaningful, tax-free savings over time. The point is not the size of the contribution — it is the principle that you are using a legal entitlement that exists specifically to help you build wealth without handing more to HMRC than you need to.

One more thing worth flagging: if you use an investment platform like Hargreaves Lansdown or Vanguard, end-of-tax-year is their busiest period. In 2025, HL processed over £1 billion in ISA contributions in the final week of the tax year. Processing times can slow, and some providers have cut-off times before 5 April to guarantee same-day settlement. Check your provider's deadline now — it may be earlier than you think.

1. Max Out Your ISA — £20,000 You Can Never Get Back

Your Individual Savings Account allowance for the 2025/26 tax year is £20,000. You can put this into a cash ISA, a stocks and shares ISA, a Lifetime ISA (up to £4,000, counts towards the £20,000), an innovative finance ISA, or any combination of these — as long as the total across all ISA types does not exceed £20,000.

Whatever you do not use by 5 April is gone. There is no rollover. If you have used £8,000 so far this tax year, you have £12,000 of allowance remaining. If you leave it unused, on 6 April 2026 you start fresh with a new £20,000 — but that £12,000 does not carry over.

Cash ISA or Stocks and Shares ISA — which one now?

If you need the money within the next three years — for a house deposit, a car, an emergency fund top-up — a cash ISA is the right move. Top rates right now are around 4.4% AER on easy-access cash ISAs, with fixed-rate options slightly higher. The interest you earn is completely tax-free, which matters especially if you already earn more than £500 a year in savings interest (the personal savings allowance for higher-rate taxpayers) or more than £1,000 (basic-rate taxpayers).

If you are investing for five or more years and are comfortable with some ups and downs in value, a stocks and shares ISA gives your money the chance to grow at a rate that historically outpaces cash over the long term. The FTSE All-World index has returned roughly 10% per year on average over the past 30 years. Inside an ISA, all of that growth and all dividends are completely free from income tax and capital gains tax, forever.

Practical steps to top up before 5 April:

Vanguard Stocks & Shares ISA — Vanguard is the UK's leading low-cost index fund provider. Their platform charge is just 0.15% per year (capped at £375), and you can open a stocks and shares ISA and fund it within 20 minutes online. For a last-minute lump sum, this is one of the most cost-effective options available.

Hargreaves Lansdown ISA — HL is the UK's largest investment platform with over 1.8 million clients. They have a same-day ISA top-up facility, and their cash ISA and stocks and shares ISA can both be opened and funded online. Their platform charge has recently been reduced from 0.45% to 0.35% — and the breadth of investment choice is unmatched.

For both platforms, you will need your National Insurance number, bank account details, and a few minutes. Transfers from your bank to your ISA on the day count as that year's contribution, provided they are settled before the end of 5 April.

If you already have an ISA from a previous provider and you want to consolidate or switch for a better rate, an ISA transfer does not count against your current year's allowance — but it does take time to process. Start a transfer request now if you want it completed before 5 April, as they can take up to 15 business days.

2. Top Up Your Pension Before Midnight on 5 April

Pensions are the most tax-efficient savings vehicle in the UK, and the end of the tax year is the last chance to maximise your contributions for 2025/26.

The basics: when you contribute to a pension, the government adds tax relief on top. If you are a basic-rate (20%) taxpayer, a £800 contribution from your bank account becomes £1,000 in your pension — the government adds £200 automatically. If you are a higher-rate (40%) taxpayer, you can claim back a further £200 through your self-assessment tax return, making a £1,000 pension contribution effectively cost you just £600.

This is not a loophole. It is specifically designed to encourage retirement saving, and it is one of the most generous financial benefits available to UK adults.

How much can you contribute?

The pension annual allowance for 2025/26 is £60,000, or 100% of your earnings — whichever is lower. Most people earn less than £60,000, so in practice the limit is your total salary. If you earn £30,000, you can contribute up to £30,000 to pensions this tax year (including your employer's contributions).

The carry forward rule — a powerful trick most people miss

If you have not used your full pension allowance in the previous three tax years, you can carry that unused allowance forward and add it to this year's limit. The carry forward rules have been particularly valuable since the annual allowance was raised from £40,000 to £60,000 in April 2023 — meaning many people have a significant backlog of unused allowance.

For example, if you contributed nothing to a personal pension in 2022/23, 2023/24, or 2024/25, you could theoretically contribute a very large lump sum this tax year (subject to your earnings limit). This is particularly useful for business owners, freelancers, and anyone who received a bonus, inheritance, or sold an asset this year.

Where to contribute

If you have a workplace pension, contact your HR or payroll team about making an additional contribution before 5 April. If you have a Self-Invested Personal Pension (SIPP), you can contribute directly online. Providers like Vanguard, Hargreaves Lansdown, and PensionBee all offer SIPPs that can be topped up online within minutes. Again, check their end-of-year cut-off times.

If you are self-employed and have not yet set up a pension, a SIPP takes about 20 minutes to open online. Even a £1,000 contribution before 5 April means £1,250 in your pension (after 20% tax relief) and costs only £600 net if you are a higher-rate taxpayer.

3. Use Your Capital Gains Tax Allowance (It's Only £3,000)

Capital Gains Tax (CGT) is the tax you pay when you sell an asset — such as shares, investment funds, cryptocurrency, or a second property — for more than you paid for it. The good news is that every individual has an annual CGT exemption: gains up to £3,000 in the 2025/26 tax year are completely tax-free.

The bad news is that the allowance has been dramatically cut in recent years — it was £12,300 as recently as 2022/23 — and unused CGT exemption cannot be carried forward. Use it or lose it, just like the ISA.

What can you do before 5 April?

If you hold investments outside an ISA or pension — in a general investment account — and some of those investments are sitting on a gain, you can sell up to £3,000 of gains before 5 April to crystallise them tax-free. If you want to stay invested, you can immediately repurchase the same investment inside your stocks and shares ISA — this is called a "bed and ISA" transaction, and it is perfectly legal and widely practised.

The mechanics of a bed and ISA: you sell the holding in your general investment account, realising a gain (up to £3,000 tax-free), and simultaneously or immediately afterwards buy the same holding inside your ISA. You stay invested, but going forward any future gains will be sheltered from CGT entirely.

If you hold cryptocurrency, the same principle applies. Selling crypto at a gain of up to £3,000 before 5 April costs you nothing in CGT. If you hold it in a general account and have unrealised gains, consider whether it makes sense to take some of those gains now within the free allowance.

4. Claim Marriage Allowance and Other Tax Breaks You Might Be Missing

The Marriage Allowance is one of the UK's most under-claimed tax breaks. Around 2.4 million couples are eligible but have never claimed, according to HMRC — meaning they are collectively leaving hundreds of millions of pounds a year on the table.

How it works:

If one partner earns less than £12,570 (the Personal Allowance) and the other is a basic-rate taxpayer (earning between £12,571 and £50,270 in England, Wales, or Northern Ireland), the lower earner can transfer £1,260 of their unused Personal Allowance to their partner. This reduces the higher earner's tax bill by up to £252 a year.

You claim via HMRC's website at gov.uk, and crucially, you can backdate a claim for up to four tax years. That means if you were eligible in 2021/22, 2022/23, 2023/24, and 2024/25, and you claim before 5 April 2026, you could receive a lump sum of up to £1,008 in tax rebates, plus this year's £252. A total of £1,260 for 15 minutes of form-filling.

Other allowances worth checking before 5 April:

The Trading Allowance gives anyone with income from self-employment, selling on eBay, doing odd jobs, or renting out a driveway up to £1,000 a year tax-free. If your trading income is under £1,000, you do not even need to file a self-assessment return for it.

The Rent a Room Scheme lets you earn up to £7,500 a year tax-free from renting out a room in your main home. If you have a lodger or have been renting a room through Airbnb, make sure you are claiming this relief — you will need to register for self-assessment if you have not already.

Dividend Allowance: if you receive dividends from investments held outside an ISA, your tax-free dividend allowance for 2025/26 is £500. Dividends above this are taxed at 8.75% (basic rate) or 33.75% (higher rate). One more reason to move investments inside your ISA before the end of the tax year.

5. Sort Your Children's Junior ISA and Savings

If you have children under 18, they each have a £9,000 Junior ISA allowance for the 2025/26 tax year. Like adult ISAs, this is a use-it-or-lose-it annual allowance — unused amounts cannot be rolled over.

Money inside a Junior ISA grows completely tax-free — no income tax on interest, no capital gains tax on growth. The child cannot access the money until they turn 18, at which point the Junior ISA automatically converts to an adult ISA, giving them a head start on their own financial future.

Junior ISA vs children's savings account — which is better?

If your child already has a Child Trust Fund (the government scheme that ran from 2002 to 2011), you can transfer it to a Junior ISA for free — and most providers make this straightforward online. Many CTFs are sitting in low-interest cash accounts, and transferring to a stocks and shares Junior ISA could make a meaningful difference over the coming years.

To open or top up a Junior ISA before 5 April, you can use providers such as Moneybox — which offers a straightforward Junior stocks and shares ISA and is particularly popular with first-time savers thanks to its round-up feature.

Frequently Asked Questions

Q: Can I open a new ISA and still use my 2025/26 allowance before 5 April? A: Yes. You can open a new ISA right up until 5 April 2026 and fund it with up to £20,000. Most major providers let you open and fund an ISA entirely online within 20–30 minutes. You will need your National Insurance number and bank account details. Just be aware that some providers have internal cut-off times on 5 April itself — check with your chosen provider.

Q: I have multiple ISAs from previous years. Does opening a new one affect my old ones? A: No. You can hold multiple ISAs from different tax years simultaneously. The rule is simply that you can only pay into one of each type of ISA per tax year during the current year. Previous years' ISAs can sit untouched and continue to grow tax-free while you open or contribute to a new one.

Q: What happens if I accidentally overpay into my ISA? A: If you pay in more than £20,000 in a single tax year across all your ISAs, HMRC will contact you and the excess will be returned. It is worth keeping a running total if you have contributed to more than one ISA this year. Most providers will warn you before you exceed the limit.

Q: Is it worth contributing to a pension if I am close to retirement? A: Generally yes, as long as you will not need the money before age 57 (the minimum pension access age from 2028). Even a short-term pension contribution attracts immediate tax relief — a 20% taxpayer gets a 25% boost on every pound contributed. Speak to a financial adviser if you are unsure about your specific situation.

Q: My spouse doesn't work. Can they still have an ISA? A: Absolutely. Every UK adult — regardless of whether they are employed — gets their own £20,000 ISA allowance. A non-working spouse can contribute up to £20,000 into their own ISA using money from a joint account or transferred from your account. This means a married couple can shelter up to £40,000 per year in ISAs between them.

Take five minutes right now to decide which of these five actions you can do before 5 April. Even if you only manage one — topping up your ISA by £100, or making a small pension contribution — you are making a decision to use what the tax system offers you. These allowances exist precisely to help ordinary UK adults build wealth. Use them.