Self Assessment pension tax relief: claim it correctly and don’t leave it too late

If you pay higher-rate Income Tax, making an additional pension contribution before the end of the tax year could save you a considerable amount of money.

But there’s a problem. By the time you know exactly how much you earned, you may have only a few days left to act. And if you leave the calculation until you prepare your Self Assessment tax return, it could be too late.

Let me explain.

The pension contribution deadline you shouldn’t miss

Earlier this year, I worked out how much I needed to pay into my pension to avoid paying 40% Income Tax on part of my income.

I did the calculation on 26th March 2026 and paid the money into my pension on 2nd April, just three days before the end of the tax year.

I’ve been doing this for nearly 20 years. Even so, getting the figures right takes some effort.

The difficulty is that you need a reasonably accurate picture of your income for the entire tax year before deciding how much to pay into your pension.

If you’re employed, that might mean waiting for your final March payslip. You’ll also need to account for other taxable income, such as bank interest, dividends or rental profits. That means adding them all up ready for your calculation.

My starting point is a printout of the previous year’s Self Assessment tax calculation (SA302). I work through the figures, updating them to reflect my income for the current year. In my case, I even had to estimate some bank interest that wouldn’t be credited until 1st April.

So, although you can take a guess at the pension contribution you need yo make throughout the year, if you want to get to the “perfect” figure, the final calculation may have to wait until late March.

That could leave you with a window of around ten days to make your payment to your pension provider before 5th April.

Why your Self Assessment tax return may be too late

Here’s what worries me.

Many people who use accountants don’t send in their Self Assessment information until months after the tax year has ended.

That’s perfectly normal. Unfortunately, by that time they will have missed the opportunity to make a final pension contribution for that previous tax year.

Your accountant can still claim any pension tax relief you’re entitled to when preparing your return. However, you cannot make a new pension contribution and backdate it to the previous tax year.

This is why pension tax planning needs to happen before 5th April, not after, when your self assessment tax return is actually prepared.

How much higher-rate pension tax relief should you claim?

There’s another complication that can catch people out.

With a personal pension operating what’s called relief at source, your pension provider claims basic-rate tax relief from HMRC and adds it to your pension pot. This normally happens about six weeks after you make the contribution.

For example:

• You pay £16,000 into your pension.
• Your pension provider claims £4,000 in basic-rate tax relief.
• Your pension receives a total contribution of £20,000.

If you pay 40% Income Tax on at least £20,000 of your income, you can generally claim a further £2,000 in tax relief through Self Assessment.

That means you’ve added £20,000 to your pension at a net cost of £12,000.

But you need to enter the correct amount on your tax return to claim the full relief.

Where do you claim pension tax relief on Self Assessment?

If you’re claiming higher-rate pension tax relief through Self Assessment, you’ll need to complete the pension contributions section under ‘Tax reliefs’.

On the 2025/26 paper tax return (SA100), this is box 1 on page TR 4. However, most people already submit their returns online, and the introduction of Making Tax Digital for Income Tax means that increasing numbers of self-employed people and landlords now use compatible software rather than paper forms.

Here’s the important part: you must enter the gross pension contribution, including the basic-rate relief claimed by your pension provider.

In our example, that’s £20,000, not the £16,000 you actually paid.

Entering £16,000 instead could mean missing out on £800 of higher-rate tax relief.

If you’ve made a one-off contribution that you don’t intend to repeat in the following tax year, you should also include it in box 1.1.

These instructions apply to pensions using relief at source. If your contributions are deducted from your pay before Income Tax, you’ve normally received the tax relief already and shouldn’t enter those contributions in this section.

The worked example also assumes you’re subject to the 40% higher rate in England, Wales or Northern Ireland. Scottish Income Tax rates are different.

Plan ahead, then check your figures in March

You don’t have to leave everything until the last minute.

My suggestion is to review your income and pension contributions well before the end of the tax year. You can then refine the figures once your March pay and other income become clearer.

You’ll also need to check that you have sufficient pension allowances available and that the contribution is appropriate for your circumstances. Our guide to pension top-ups explains some of the limits.

Most importantly, allow enough time for your pension provider to receive your payment before the deadline.

Talk to THP before 5th April

If you’re likely to pay higher-rate Income Tax, it’s worth speaking to your accountant before the tax year ends.

At THP, we can help you estimate your final tax position, calculate the effect of an additional pension contribution and make sure you claim the relief you’re entitled to. We can also work alongside your pensions adviser where appropriate.

The lesson is simple: your Self Assessment return tells you what happened last year. Good tax planning helps you do something about it while there’s still time.

If you’d like help reviewing your position, contact our tax planning specialists before the end of the tax year.