How do Self Assessment payments on account work?
Payments on account are advance payments toward your next year's tax bill, and they catch out almost every first-time filer. If your Self Assessment bill is over £1,000 and less than 80% of your tax was collected at source, HMRC asks you to pay your current bill plus a payment on account equal to 50% of it — and another 50% in July. So a first £3,000 bill can become £4,500 due in January. It is not a penalty or double taxation; you are paying ahead. If you know next year's income will be lower, you can apply to reduce the payments (GOV.UK).
The worked example — a £3,000 bill becomes £4,500
You complete your 2025/26 return and the tax owed is £3,000. Here is what HMRC actually asks for, and when.
2025/26 tax year · cash-out schedule
31 January 2027
£3,000 balancing payment for 2025/26 + £1,500 first payment on account for 2026/27
£4,500
31 July 2027
Second payment on account for 2026/27
£1,500
Total cash out by July 2027
But £3,000 of that is pre-paying 2026/27 — not extra tax.
£6,000
Source: GOV.UK — Understand your Self Assessment bill: payments on account.
When do payments on account apply?
| Condition | Threshold |
|---|---|
| Tax bill above | £1,000 |
| Tax already collected at source (e.g. PAYE) | < 80% |
Both conditions must be true. If either fails, payments on account do not apply for that year. Source: GOV.UK — Pay your Self Assessment bill: payments on account.
How payments on account actually work
The mechanic is straightforward once you see it on a timeline. HMRC assumes next year's tax bill will look broadly like this year's, and asks you to pay it in two equal instalments — one on 31 January (alongside the balancing payment for the year just gone) and one on 31 July (GOV.UK).
When you actually file the next year's return, HMRC totals up what you have already paid through the two payments on account, compares it with your actual liability, and either bills you for the balance or refunds the difference. Then the cycle starts again: the new bill drives the next year's payments on account.
Two things to keep separate in your head:
- Income tax and Class 4 NIC are included in payments on account.
- Capital gains tax and student loan repayments are not — they sit only with the balancing payment.
The 1.5x first-year shock
In year one, you owe the full balancing payment for the year just gone plus the first payment on account for the year ahead — both due on the same 31 January. That is where the "1.5x" feeling comes from: a £3,000 bill turns into a £4,500 demand, and then another £1,500 in July. By July you have paid out £6,000 — but £3,000 of that is pre-paying the next year, not extra tax for the old one.
From year two onward, the shock fades. Each January you pay the balancing figure (which is now usually smaller because the prior July payment on account ate into it) plus the first instalment for the new year. The cadence smooths out — you are just paying tax closer to when you earned it.
Most of the panic emails accountants get on 27 January are from first-time filers who saw the £4,500 number, assumed an HMRC error, and Googled it at midnight. There is no error — it is the regime working as designed.
Reducing payments on account with form SA303
The default assumption — that next year's bill looks like this year's — is wrong often enough that HMRC built an escape hatch. If you can show that your taxable income will genuinely be lower next year, you can apply to reduce the payments on account. The mechanism is form SA303, or the equivalent reduction request inside your online Self Assessment account (GOV.UK).
Sensible reasons to reduce:
- You have closed a side business or sold a property.
- A major contract has ended and you have not replaced it.
- You have moved to PAYE employment with most tax now deducted at source.
- Your profits have dropped materially and the previous year was an outlier.
Don't under-claim
If you reduce payments on account and your actual bill comes in higher than the reduced amount, HMRC charges interest on the shortfall from the original due dates — and in careless cases, a penalty too. Base the reduction on a realistic forecast, not on optimism.
Budgeting for the cycle
The cleanest discipline is to treat your tax as someone else's money the moment it lands in your bank account. Put aside a percentage of every invoice — typically 25–30% for a basic-rate sole trader, more if you are higher-rate — into a separate account, and pay HMRC from that account. Once you have done one full cycle, you will know exactly what your number is.
Two practical habits that make payments on account painless:
- File early. Filing in May or June (not January) tells you the exact bill nine months ahead. You can budget the £4,500 and the £1,500 instead of being ambushed by it.
- Set the dates as cash-flow events, not tax dates. 31 January and 31 July are payment dates, not just filing reminders. Put both in your business calendar with the amount.
Payments on account are NOT extra tax
They are timing. But the cash-flow hit is real — and that is exactly the kind of thing an accountant flags before it lands, not after.
A note for company directors
If you take significant dividends from your limited company, payments on account apply to dividend tax too — and directors often feel the 1.5x January shock the hardest the first year they cross the £1,000 threshold. See Salary vs dividend: how to pay yourself from a UK limited company for the planning side of that decision, and Self Assessment for company directors for what actually goes on the return.
Want to estimate your number?
The fastest way to see what your January bill will look like — and whether payments on account will trigger — is to run the figures through the Self Assessment tax calculator. It gives you a rough number in seconds; we file the actual return.
Frequently asked questions
What are Self Assessment payments on account?
Payments on account are advance instalments toward your next year's Self Assessment tax bill. You pay them in two halves — 50% of the prior year's bill on 31 January (alongside your balancing payment) and another 50% on 31 July. They are not extra tax; they are a timing mechanism to move you toward paying tax closer to when you earn it.
Why is my first Self Assessment bill 50% bigger than I expected?
Because the first time you cross the £1,000 threshold, HMRC asks for the balancing payment for the year just gone plus a first payment on account equal to 50% of that bill — both due on 31 January. A £3,000 bill becomes £4,500 due in January. You then pay another £1,500 on 31 July. From year two onward, the rhythm smooths out because you have already pre-paid.
Who has to make payments on account?
You make payments on account if your Self Assessment tax bill is more than £1,000 and less than 80% of your tax was already collected at source — typically through PAYE. If your tax is mostly deducted at source already (a salaried employee with a small side income, for example), payments on account often will not apply.
Can I reduce my payments on account?
Yes — if you genuinely expect your income (and therefore your tax bill) to be lower next year, you can ask HMRC to reduce the payments. The claim is made on form SA303 or through your online Self Assessment account. Be honest with the estimate: if you under-claim and your actual bill is higher, HMRC charges interest on the shortfall from the original due date.
What is form SA303?
SA303 is the formal claim to reduce your Self Assessment payments on account. You submit it when you reasonably expect lower income — for example because you have closed a side business, dropped to part-time, or lost a contract — and you want to avoid pre-paying tax you won't owe. You can file it on paper or via your online HMRC account.
What happens if I reduce my payments and was wrong?
If you reduce payments on account and your actual tax bill comes in higher than the reduced amount, HMRC charges interest on the shortfall, calculated from the original due dates (31 January and 31 July). In some cases there may also be a penalty if the reduction was claimed carelessly. The fix is to base any reduction on a realistic forecast — and to top up early if you see income picking back up.
When do payments on account go away?
Payments on account stop being required for a tax year if your final bill for that year drops below £1,000, or if 80% or more of your tax is collected at source. If you stop trading or your income falls back below the threshold, the next year's bill will not include payments on account — and any pre-paid amounts that exceed your final liability are refunded or rolled forward.
Do payments on account apply to capital gains tax?
No. Payments on account cover your income tax and Class 4 National Insurance, but they do not include capital gains tax. CGT is paid as a one-off on 31 January with your balancing payment (or, for UK residential property, within 60 days of completion via the dedicated CGT-on-property service). Student loan repayments collected via Self Assessment are also excluded from payments on account.
The full Self Assessment series
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About the author
Mehmood Rajoka, Managing Partner, RR Accountants
Managing Partner at RR Accountants — a UK practice supervised by the Institute of Financial Accountants. Specialist focus on Self Assessment, director tax planning, and MTD for Income Tax. RR Accountants files Self Assessment returns from £150+VAT with a 48-hour turnaround.
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This guide is general information about UK tax rules. It is not personal tax advice. For advice tailored to your situation, speak to a regulated UK accountant. All figures verified against gov.uk as of . Payment-on-account thresholds and HMRC interest rates are reviewed periodically — re-check primary sources before acting.