UK Tax Year End Checklist: 6 Things to Do Before 5 April
The UK tax year ends on 5 April, and several allowances are "use it or lose it". If you've got some spare savings, or your income is close to a tax threshold, a couple of hours before the deadline can save you real money. Here's a checklist for the 2025/26 tax year, in rough order of how many people it helps.
1. Use your ISA allowance
You can put up to £20,000 a year into ISAs, split however you like across cash, stocks and shares, innovative finance and Lifetime ISAs. Interest, dividends and gains inside an ISA are tax-free, and unused allowance doesn't roll over.
- Lifetime ISA: if you're 18–39 when you open it, you can pay in up to £4,000 a year (counting towards the £20,000) and the government adds a 25% bonus, up to £1,000. It's for a first home or retirement, and withdrawing for anything else normally costs a 25% charge.
- Junior ISA: up to £9,000 per child, on top of your own allowance.
- Coming change: the government has announced that from April 2027 the cash ISA limit will drop to £12,000 a year for people under 65, with the overall £20,000 limit unchanged. It doesn't affect this year's allowance.
2. Top up your pension
Pension contributions get tax relief at your highest rate of income tax. Most people can contribute up to the £60,000 annual allowance (or 100% of their earnings, if lower). Unlike ISAs, you can usually carry forward unused allowance from the previous three tax years, as long as you were in a registered pension scheme in those years.
For basic-rate taxpayers, a £100 contribution effectively costs £80. Higher-rate taxpayers can claim back a further £20 through Self Assessment, making it £60. That's before any employer contribution.
3. Watch the £100,000 trap
If your adjusted net income goes above £100,000, you lose £1 of your £12,570 personal allowance for every £2 over. Between £100,000 and £125,140 that creates an effective income tax rate of 60% (plus National Insurance). Crossing £100,000 can also cost parents their Tax-Free Childcare and some funded childcare hours.
A pension contribution, or a salary sacrifice arrangement, reduces adjusted net income and can bring you back below £100,000, rescuing both the allowance and the childcare support. Check where your pay lands with the UK salary after tax calculator.
4. Claim the marriage allowance
If you're married or in a civil partnership and one of you earns less than the personal allowance while the other is a basic-rate taxpayer, the lower earner can transfer £1,260 of their allowance. That's worth up to £252 a year, and you can backdate a claim for up to four previous tax years if you were eligible. It's free to apply on GOV.UK.
5. Use your capital gains and dividend allowances
- Capital gains: the annual exempt amount is £3,000. If you hold investments outside an ISA with gains, selling enough to use the allowance, then rebuying inside an ISA ("Bed and ISA"), can shelter future growth.
- Dividends: the first £500 of dividends outside ISAs and pensions is tax-free. Above that, it's taxed at dividend rates.
- Savings interest: the personal savings allowance lets basic-rate taxpayers earn £1,000 of interest tax-free, or £500 for higher-rate taxpayers. With higher rates in recent years, it's easier to go over than it used to be, another reason to use cash ISAs.
6. Tidy up the admin
- Check your tax code on your payslip or in your HMRC account. Wrong codes are common after a job change.
- Gift Aid: higher-rate taxpayers can claim extra relief on donations.
- Keep records of pension contributions, donations and any side income for your Self Assessment return.
- Know your National Insurance position. Rates and thresholds are summarised in National Insurance rates 2026.
Don't leave it until 5 April itself
Transfers into ISAs and pensions can take a few working days to go through, and some providers set their own cut-offs before the end of the tax year. Aim to have everything done by the last week of March.
Tax rules change, and your circumstances matter. If you're dealing with large sums, pensions carry-forward or the £100,000 threshold, it's worth speaking to a regulated financial adviser or accountant.
Frequently asked questions
When does the UK tax year end?
On 5 April. The new tax year starts on 6 April.
How much can I put in an ISA this tax year?
£20,000 across all your ISAs. A Lifetime ISA can take up to £4,000 of that, with a 25% government bonus.
What is the 60% tax trap?
Between £100,000 and £125,140 of adjusted net income, your personal allowance is withdrawn at £1 for every £2 earned, creating an effective 60% income tax rate. Pension contributions can reduce it.
Can I backdate the marriage allowance?
Yes, for up to four previous tax years if you were eligible, as well as claiming it for the current year.