Tax year-end planning

A handful of allowances reset every 5 April. Unused, they're simply gone.

The tax year ends on 5 April, and with it a set of allowances that don't carry forward. Anything you haven't used by then is gone permanently — not deferred, not banked, gone.

Most of what follows takes an evening. The reason it doesn't get done is that there's no deadline pressure until suddenly there is.

The ones that vanish

ISA allowance — £20,000. The largest and most valuable. Every year you don't use it is a year of tax-free capacity lost forever. You can't put £40,000 in next year to make up for it.

Capital gains annual exempt amount — £3,000. Realise gains up to this each year and pay nothing. Do nothing, and you've wasted it while your unrealised gain grows towards a larger eventual bill.

Dividend allowance — £500 and Personal Savings Allowance — £1,000 or £500. Both reset, neither carries forward.

The Personal Allowance itself — £12,570. Most relevant to anyone with low taxable income and flexibility over what they draw. A retiree living entirely off ISA withdrawals wastes this every year, which is the whole subject of Which pot do you spend first?.

Annual gifting exemptions for inheritance tax — the annual exemption plus small gifts and gifts on marriage. The annual exemption can be carried forward one year only, and no further.

Junior ISA allowance for each child.

The ones with a longer window

Pension Annual Allowance — £60,000. This one does carry forward, for three years. But the oldest year drops off every 5 April, so if you have unused allowance from three years back and intend to use it, this is the deadline. See Carry forward.

Marriage Allowance can be backdated four years, so there's no urgency — but people who mean to claim it often still haven't.

Higher-rate pension tax relief in relief-at-source schemes can usually be claimed back several years. Again, no cliff edge, but worth doing.

A sensible order

Rather than working through the list, work through the value:

Employer pension matching. If you're contributing below the level your employer will match, you're declining part of your pay. Nothing else on this list beats it.
Anything that pulls you out of a cliff edge. If your income is near £100,000, or near £60,000 with children, a pension contribution before 5 April is worth far more than its headline relief. See The 60% tax trap and the Child Benefit charge.
ISA allowance, as much of it as you can manage.
Use the capital gains exemption. Realise gains up to £3,000, and consider bed and ISA to move holdings inside a wrapper permanently.
Pension contributions generally, including carry forward if you have unused allowance about to expire.
Gifting exemptions, if inheritance tax is a consideration.

A rhythm that works better

Doing all of this in the last week of March is how it gets rushed, and how investment decisions get made on a deadline rather than on merit.

Two alternatives:

Monthly. Standing orders into ISAs and pensions spread the cost, remove the decision, and mean you're buying at a range of prices rather than one. The allowance takes care of itself.

A November review. Look at the position with four months to go, decide what needs doing, and act with time to spare. Anything requiring a form, a transfer, or a conversation with a provider needs longer than you think, and providers are at their busiest in late March.

The one genuine deadline trap

Transfers and applications submitted close to 5 April may not complete in time, and it's the completion date that counts for most allowances, not the date you sent the form. Providers routinely publish cut-off dates in mid to late March for this reason.

If you're planning something that requires a provider to act — opening an account, transferring money in, executing a bed and ISA — assume it needs to be started weeks rather than days in advance.

This article is for general education only and isn't personal advice. Figures are for 2026/27.