ISA Deadline 2026: Use Your £20,000 Allowance Before April 5th

Every year, without fail, April 5th arrives and millions of pounds of ISA allowance vanishes unused. Not lost to bad investments. Not spent on something worthwhile. Just gone — because people meant to get round to it and didn't quite make it in time.

This year the deadline is Saturday 5th April 2026. That gives you less than four weeks. If you have money sitting in a current account or easy-access savings account earning taxable interest, this is the most straightforward financial action you can take right now — move it into an ISA before the deadline and shelter it from tax permanently.

What the ISA Allowance Actually Is

Every UK adult gets a fresh £20,000 ISA allowance at the start of each tax year on April 6th. Anything you put inside an ISA grows free of income tax and capital gains tax — forever. You never pay tax on the interest, dividends, or growth, no matter how large the pot becomes.

The critical bit most people miss: the allowance is use it or lose it. If you put in £8,000 this tax year and the deadline passes, you cannot go back and top it up with the remaining £12,000. That headroom is gone. The new tax year brings a fresh £20,000, but the old one does not carry over.

You can split the £20,000 across multiple ISA types in the same tax year — for example £4,000 into a LISA and £16,000 into a Stocks & Shares ISA — as long as the total does not exceed £20,000.

Who Should Definitely Use Their Allowance Before April 5th

Not everyone is in the same position, so here is a straightforward breakdown of who should act now and who can be more relaxed about it.

Higher and additional rate taxpayers with savings

If you earn over £50,270, your personal savings allowance is just £500 per year. Any interest above that is taxed at 40%. With savings rates still relatively decent, even a £25,000 pot in a standard savings account could easily generate £1,000+ in interest — half of which gets taxed away. Moving that money into a Cash ISA or Stocks & Shares ISA before April 5th eliminates that tax bill entirely and permanently.

Take Sarah, a project manager in Birmingham earning £62,000. She has £30,000 sitting in an easy-access savings account at 4.5% — generating £1,350 in interest per year. As a higher rate taxpayer with only a £500 savings allowance, she pays 40% tax on £850 of that interest — £340 a year in unnecessary tax. Moving £20,000 into a Stocks & Shares ISA before April 5th and the remaining £10,000 in the next tax year would shelter all of that interest from tax within two years.

Anyone sitting on uninvested cash earmarked for the long term

If you have money you know you will not need for five or more years — money you keep meaning to invest but have not got around to — putting it into a Stocks & Shares ISA before the deadline is a meaningful action. You do not have to decide exactly what to invest in immediately. Many providers let you open an ISA, deposit the cash before April 5th to lock in the allowance, and then choose your investments at your leisure after the deadline.

Basic rate taxpayers with over £1,000 in savings interest

Basic rate taxpayers get a £1,000 personal savings allowance, which sounds generous until you do the maths. At 4.5%, you would need only around £22,000 in savings to exceed it. If your savings pot is above that level, you are already paying income tax on interest unnecessarily. An ISA fixes that.

Under-40s who have not opened a LISA yet

The Lifetime ISA is only available to people aged 18–39. If you are 39, this could literally be your last year to open one. The government adds a 25% bonus on contributions up to £4,000 per year — that is up to £1,000 of free money annually for either a first home purchase or retirement. Even putting in £1 before April 5th opens the account and preserves your eligibility. There is almost no scenario where a 39-year-old with any spare money should not do this.

ISA vs Pension: Which Should You Use Before April?

This is the question worth spending a minute on, because the answer is not the same for everyone.

For most employed people with a workplace pension, the priority order looks like this:

1. Employer pension match first. If your employer matches contributions up to a certain percentage and you are not hitting that threshold, maximise it before anything else. It is a guaranteed 100% return that neither an ISA nor anything else can compete with.
2. ISA second, if you are a higher rate taxpayer with taxable savings. The tax saving is immediate and certain.
3. Pension above the match third. Additional pension contributions give you income tax relief — 20% for basic rate, 40% for higher rate — which is a better guaranteed return than most investments. But the money is locked until 57 (rising to 57 in 2028). ISA money is accessible at any time, which matters if you might need flexibility.

The ISA wins over a pension when you want flexibility — money you might need before retirement, want to pass on outside of an estate, or want to draw without worrying about income tax on withdrawals. The pension wins when you want the tax relief upfront and are confident about not needing the money until retirement.

For a deeper comparison of how these two work together, see our full pension vs ISA guide.

The Most Common Mistake People Make

Leaving it too late and then rushing into the wrong thing.

Every year in the days before April 5th, people panic and dump money into a Cash ISA paying 3% when they would have been better off in a Stocks & Shares ISA. Others pour the full £20,000 into an ISA and leave themselves without an emergency fund. Neither of these is a good outcome.

The right approach is simple. First, make sure your emergency fund is solid — three to six months of expenses in an accessible account. Then look at what is left. If it is money you will not need for five or more years, a Stocks & Shares ISA invested in a low-cost global index fund is almost certainly the right home for it. If you might need it within five years, a Cash ISA or easy-access cash ISA makes more sense.

The important thing is not to let perfect be the enemy of good. Even putting £5,000 into a Stocks & Shares ISA before April 5th and deciding later exactly how to invest it is better than missing the deadline and losing the allowance entirely.

What to Do Right Now

1. Check how much ISA allowance you have used this tax year. Log into your ISA provider or check your statements. If you have used £0, you have the full £20,000 available.
2. Decide how much you can realistically put in before April 5th without touching your emergency fund or money you need short-term.
3. If you do not have an ISA yet, open one today. Most providers — Vanguard, Hargreaves Lansdown, AJ Bell, Moneybox — take less than 15 minutes to open online.
4. If you are under 40 and do not have a LISA, open one immediately. Even a £1 contribution before April 5th preserves your eligibility.
5. Transfer money in before April 5th. Bank transfers usually clear within 1–3 working days, so do not leave it until the last minute.