Understanding Your Self Assessment Tax Bill

When you file your Self Assessment tax return, HMRC sends you two important documents: a Self Assessment statement (your bill) and a tax calculation (known as an SA302). Understanding what these documents show — and the difference between them — is essential to making sure you pay the right amount on time and avoid penalties.

The two documents you'll receive

After you submit your Self Assessment tax return, you receive two separate documents that serve different purposes.

Your Self Assessment statement is your actual bill. It shows what you owe at the time the statement is sent, including any payments on account due, payments you've already made (shown as 'CR' on the statement), any outstanding amounts from previous tax years or interest, and your balancing payment if applicable.

Your tax calculation (also called an SA302 or tax computation) shows how HMRC has worked out your tax liability for the tax year. It includes your total income on which tax is due, any allowances and reliefs you have, the total amount you owe for the tax year, and how HMRC calculated this amount.

The key difference is that your tax calculation shows only the tax for that specific tax year. It does not include payments on account you've made, payments into a Budget Payment Plan, or other outstanding amounts such as unpaid tax or penalties from previous years.

When you'll receive these documents

You'll receive your statement and tax calculation after you file your tax return or if your circumstances change. If you file online, you can view your tax calculation in your online account before you submit your return.

After you submit an online return, you cannot view your calculation for up to 72 hours. If your payment is due during this time, save a copy of your calculation before submitting.

If you file a paper return, HMRC will send your calculation by post.

If you submit your tax return late or close to the 31 January deadline, you may not receive your Self Assessment statement before your payment is due. In this case, check your online account and view your current balance to work out how much you owe.

Understanding payments on account

Payments on account are advance payments towards your next tax bill (including Class 4 National Insurance if you're self-employed). They help spread the cost of your tax across the year by splitting it into two instalments.

Each payment on account is half of the tax you owed last year. These payments are due by midnight on 31 January and 31 July.

You must make these two payments unless either:

• The amount of tax you owed last year was less than £1,000
• Last year you paid more than 80% of the tax you owed outside of Self Assessment (for example through your tax code or because your bank deducted interest on your savings)

Your Self Assessment statement or online account will show whether you need to make payments on account and how much they are.

What is a balancing payment?

Payments on account are based on your estimated earnings (usually the amount you earned the previous year). If you actually earn more than estimated, you'll still have tax to pay on top of your payments on account. This additional amount is called a balancing payment.

The balancing payment is worked out by deducting the payments on account you've made from the total tax you owe. You must pay this by midnight on 31 January the following year. This will also include anything you owe for capital gains or student loan repayments (if you're self-employed).

If you earn less than estimated, you may be able to claim a tax refund.

Your first year making payments on account

If you did not make any payments on account last year (for example, because it's your first time filing Self Assessment), you'll need to pay both the full amount of your tax calculation and your first payment on account towards your next bill.

Here's an example: Your bill for the 2023 to 2024 tax year is £3,000. The total tax to pay by midnight on 31 January 2025 would be £4,500. This includes your £3,000 tax bill for 2023 to 2024 and the first payment on account of £1,500 (half your 2023 to 2024 tax bill) towards your 2024 to 2025 tax bill.

You then make a second payment on account of £1,500 on 31 July 2025.

If you've been making payments on account

If you made payments on account last year, you'll need to pay both your first payment on account towards your next bill and any balancing payment you owe (if you still have tax to pay after last year's two payments on account).

Here's an example: Your bill for the 2023 to 2024 tax year is £3,000. Based on your 2022 to 2023 earnings, you made two payments of £900 each (£1,800 in total) on 31 January 2024 and 31 July 2024 towards this — these were your payments on account.

Because your payments on account did not cover the amount of tax you owed, you have to make a balancing payment.

Your amount due by midnight on 31 January 2025 is made up of:

• Your balancing payment of £1,200 for the 2023 to 2024 tax year (£3,000 minus £1,800)
• The first payment on account of £1,500 (half your 2023 to 2024 tax bill) towards your 2024 to 2025 tax bill

This means the total you will have paid is £2,700 by 31 January 2025.

You then make a second payment on account of £1,500 on 31 July 2025.

If your tax calculation for the 2024 to 2025 tax year is more than £3,000 (the total of your two payments on account), you'll need to make a balancing payment by 31 January 2026.

Checking your calculation is correct

When you receive your tax calculation, check that HMRC has included all your income, allowances, and reliefs correctly. If you filed online, you would have seen a preview of your calculation before submitting your return.

Look through each section carefully to ensure the figures match what you reported on your tax return. Check that your Personal Allowance and any other tax reliefs have been applied correctly.

Payment deadlines and penalties

You need to pay your Self Assessment tax bill by midnight on 31 January (following the tax year you're paying for) to avoid a penalty. If you cannot pay your bill on time, contact HMRC to discuss your options.

Sources

• Understand your Self Assessment tax bill

This article provides general guidance based on current HMRC rules. For advice specific to your situation, speak to your accountant.