Self Assessment Payment on Account Calculator
Work out your 31 January balancing payment and your July payment on account for the 2025/26 UK tax year.
Last updated: 15 June 2026 (2025/26 tax year — GOV.UK verified)
Payments on account for Self Assessment 2025/26
HMRC asks most people in Self Assessment to make two advance payments — called payments on account — towards next year's bill. Each one is half of your previous year's Income Tax plus Class 4 National Insurance, due on 31 January and 31 July. You are exempt if your last bill was under £1,000 or more than 80% of your tax was already collected at source. This calculator applies those exact GOV.UK rules so you can see your balancing payment and each instalment.
Payment on Account Calculator 2025/26
Enter your total Self Assessment tax for the year and how much was already taxed at source to see your payments on account and balancing payment.
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What are payments on account?
A payment on account is an advance instalment towards your next Self Assessment tax bill. The system exists because people inside Self Assessment — typically the self-employed, landlords, company directors and higher earners with untaxed income — don't have tax taken automatically from their income the way employees do under PAYE. Rather than letting a whole year's tax build up into one large lump sum every January, HMRC asks you to pay it in two instalments, ahead of time, based on what you owed the previous year.
The logic is simple: HMRC assumes your income this year will be broadly similar to last year, so it asks for two payments that together equal last year's bill. When you eventually file and the real figure is known, the payments you have already made are deducted from it — and you either pay a balancing payment for any shortfall or receive a refund for any overpayment. Catching how this works the first time you join Self Assessment is important, because in your very first year you can face roughly 150% of a normal year's tax in a single January: the whole first-year bill plus the first payment on account towards year two.
Key payment-on-account facts (2025/26)
- Each payment: 50% of last year's Income Tax + Class 4 NI
- First instalment due: 31 January
- Second instalment due: 31 July
- £1,000 rule: no payments on account if last bill < £1,000
- 80% rule: no payments on account if >80% taxed at source
- Excluded: student loans, Class 2 NI and CGT (balancing payment only)
How this calculator works
The calculator follows the official GOV.UK test in three steps. Step one checks the two exemptions. If your total Self Assessment bill is below £1,000, or if more than 80% of your tax was already collected at source, then no payments on account are due — you simply pay the whole bill by 31 January. The 80% figure is calculated as the percentage you entered applied to your total bill; HMRC compares the tax not covered at source against the total.
Step two, where payments on account are required, takes the part of your bill that counts — your Income Tax plus Class 4 National Insurance, minus anything taxed at source — and halves it. That half is each payment on account. Step three builds your timeline: your first payment on account plus any balancing element is due on 31 January, and the second payment on account follows on 31 July.
Crucially, the calculator separates out the amounts HMRC never spreads. Student loan repayments, voluntary Class 2 NI and Capital Gains Tax are not part of the payment-on-account calculation — they are always collected in full as part of the January balancing payment. The "extra amounts not spread" field lets you add these so your total January demand is accurate, while keeping the payment-on-account maths correct. All of this runs instantly in your browser; nothing is sent anywhere.
The formula in plain terms:
Spreadable tax = Total SA tax × (1 − % at source ÷ 100)
Each payment on account = Spreadable tax ÷ 2
January demand = Balancing payment + 1st payment on account + extras
Worked example: a self-employed designer
Imagine Priya, a self-employed graphic designer. For the 2024/25 tax year she files her return and her Self Assessment bill comes to £6,000 — that's her Income Tax plus Class 4 National Insurance combined, with none of it taxed at source (she has no PAYE job). Because the bill is over £1,000 and 0% was taxed at source, both exemptions fail, so payments on account apply.
By 31 January 2026, Priya pays:
| Balancing payment for 2024/25 | £6,000 |
| 1st payment on account for 2025/26 (50%) | £3,000 |
| Total due 31 January 2026 | £9,000 |
Then on 31 July 2026, she pays her 2nd payment on account of £3,000. Together her two 2025/26 payments on account total £6,000 — exactly last year's bill.
Fast-forward: when Priya files her 2025/26 return, suppose her actual bill is £7,200 (a good year). She has already paid £6,000 in payments on account, so her balancing payment is £7,200 − £6,000 = £1,200, due 31 January 2027 — plus her first payment on account for 2026/27 of £3,600 (half of £7,200). If instead her 2025/26 bill had fallen to £4,000, she would have overpaid by £2,000 and HMRC would refund it. This is the rhythm of Self Assessment: each January is a balancing payment plus the next year's first instalment, and each July is the second instalment.
The first-year cash-flow shock
In Priya's very first Self Assessment year she paid 150% of a normal year in one January: £6,000 for the year just gone plus £3,000 advance for the next. Many new sole traders are caught out by this. Setting aside roughly 30% of profit as you earn, and using this calculator before 31 January, prevents the nasty surprise.
The rules that decide whether you pay
Rule 1 — The £1,000 threshold
Per GOV.UK, you do not have to make payments on account if "the amount of tax you owed last year was less than £1,000". This is the most common reason small or occasional Self Assessment taxpayers — a landlord with a tiny profit, someone with modest dividend income — never see a July demand. If your bill is £999 you pay it all by 31 January and that's the end of it; at £1,000 the payments-on-account machinery switches on.
Rule 2 — The 80%-at-source test
You are also exempt if "last year you paid more than 80% of the tax you owed outside of Self Assessment" — typically through PAYE on a salary, or tax deducted by a bank. This protects people whose Self Assessment liability is mostly a small top-up. A higher-rate employee with a modest amount of untaxed savings interest, for example, has the vast majority of their tax already collected by their employer, so HMRC doesn't ask for advance instalments on the small remainder.
Worked check: if your total bill is £5,000 and £4,200 (84%) was taxed at source, only £800 sits in Self Assessment — over the 80% line, so no payments on account. If only £3,800 (76%) was at source, you are under 80% and payments on account apply to the spreadable portion.
Rule 3 — What's in, what's out
Payments on account are built only from Income Tax and Class 4 National Insurance. According to the Low Incomes Tax Reform Group, student loan repayments, voluntary Class 2 NI and Capital Gains Tax are excluded from the calculation and are always collected in full as part of the 31 January balancing payment. They are also ignored when working out next year's payments on account. That's why this calculator has a separate "extras" field — it adds them to your January total without inflating your instalments.
Reducing your payments on account
If you know your income will be lower this year, you can apply to reduce your payments on account using the SA303 process through your HMRC online account. But take care: if you reduce them below what you actually owe, HMRC charges late-payment interest on the shortfall back to the original due date — currently the Bank of England base rate plus 2.5%, per the HMRC interest rates page. Only reduce to a figure you are confident reflects a genuinely lower year.
Deadlines and what happens if you miss them
For the 2025/26 tax year (6 April 2025 to 5 April 2026), the Self Assessment timeline runs as follows. Your online tax return and balancing payment, together with your first payment on account towards 2026/27, are due by midnight on 31 January 2027. Paper returns must be filed earlier, by 31 October 2026. Your second 2026/27 payment on account falls due on 31 July 2027.
HMRC's penalty regime, set out on GOV.UK, treats late filing and late payment separately. A late payment on account does not trigger the automatic £100 late-filing penalty (that applies to the return), but it does accrue late-payment interest daily from the due date. The balancing payment is subject to surcharges if left unpaid: 5% of the unpaid tax at 30 days late, another 5% at 6 months, and a further 5% at 12 months. Interest runs throughout at base rate plus 2.5%.
If you genuinely cannot pay, HMRC's Time to Pay service lets you spread the cost in instalments — it's far better to arrange this proactively than to miss the deadline silently. For a fuller breakdown of the year's key dates, see our companion UK Tax Deadlines 2026 guide.
Frequently asked questions
What is a payment on account in Self Assessment?
A payment on account is an advance payment towards your next Self Assessment tax bill. HMRC asks for two instalments, each equal to half of your previous year's Income Tax and Class 4 National Insurance, due on 31 January and 31 July. They spread your tax over the year rather than leaving one large bill, and they are deducted from next year's liability when you file.
When do I NOT have to make payments on account?
Per GOV.UK, you do not make payments on account if either your last Self Assessment tax bill was less than £1,000, or more than 80% of the tax you owed for the year was already collected at source (for example through PAYE). If either test is met, you simply pay the full balance by 31 January and no advance instalments are due.
How much is each payment on account?
Each payment on account is 50% of your previous tax year's combined Income Tax and Class 4 National Insurance liability. So if last year you owed £4,000, each payment on account is £2,000 — one due 31 January and one due 31 July, totalling £4,000 paid in advance towards the current year.
What is the balancing payment?
The balancing payment is the difference between your actual tax bill for the year and the payments on account you have already made. It is due by 31 January after the tax year ends, alongside your first payment on account for the next year. If your payments on account exceeded your bill, HMRC refunds the difference instead.
Are student loans and Class 2 NI included in payments on account?
No. Payments on account are based only on Income Tax and Class 4 National Insurance. Student loan repayments, voluntary Class 2 NI and Capital Gains Tax are always collected in full as part of the balancing payment on 31 January and are never spread across the two instalments.
Can I reduce my payments on account?
Yes. If you expect your income to fall, you can apply to reduce your payments on account through your HMRC online account or on the SA303 form. But if you reduce them too far, HMRC charges interest on the shortfall once you file, so only reduce to a figure you are confident reflects the lower year.
What happens if I pay my payment on account late?
HMRC charges late-payment interest on overdue payments on account from the due date until paid, at the Bank of England base rate plus 2.5%. There is no automatic £100 penalty on a late payment on account itself (that penalty applies to late filing), but the balancing payment can attract 5% surcharges at 30 days, 6 months and 12 months if left unpaid.
Related UK tax calculators
Payments on account are just one part of Self Assessment. Use these related tools to size up the bill they are based on:
- Self Assessment Calculator — estimate your total Self Assessment liability, the figure your payments on account are built from.
- Class 4 National Insurance Calculator — work out the Class 4 NI that, with Income Tax, makes up the spreadable amount.
- UK Tax Calculator — full income tax and National Insurance breakdown for employees, the self-employed and pensioners.
- All Calculators — browse every free UK calculator on the site.