Payments on Account Explained: How to Survive the 31 January Self Assessment Bill
Payments on account catch out thousands of UK sole traders and directors every January. Here is how they are calculated, when you can reduce them, and how to budget so the bill never bites.
Every January, HMRC's Self Assessment deadline turns a manageable tax bill into a cash-flow emergency for thousands of UK sole traders and company directors. The reason is almost always the same: payments on account.
What a payment on account actually is
A payment on account is an advance instalment towards next year's Income Tax (and Class 4 National Insurance, for the self-employed). HMRC assumes your next tax year will look like your last one, so it asks you to pay it in two instalments before the year has even finished.
- 31 January — balancing payment for the tax year just filed, plus the first payment on account for the current year.
- 31 July — the second payment on account.
Each payment on account is 50% of last year's tax liability (excluding Capital Gains Tax and student loan repayments).
Why the first January is brutal
In your first profitable year the system effectively asks for 150% of the tax due:
| Item | Amount |
|---|---|
| Tax due for the year just filed | £8,000 |
| First payment on account (50%) | £4,000 |
| Due on 31 January | £12,000 |
| Second payment on account (31 July) | £4,000 |
Nobody budgets for £12,000 when their tax calculation said £8,000. That single mismatch is the most common reason UK sole traders end up on a Time to Pay arrangement.
When you do not have to make payments on account
You are outside the regime if either of the following applies:
- Your last Self Assessment liability was under £1,000, or
- 80% or more of your tax was already collected at source (PAYE, or tax deducted from savings and dividends).
That second test matters for directors: if most of your income is a PAYE salary and only a slice is dividends, you may fall outside payments on account entirely.
Reducing your payments on account — carefully
If you know this year's profits will be materially lower, you can apply to reduce the payments (form SA303 or directly in your HMRC online account). Good reasons include:
- Losing a major client or contract
- Moving from sole trader to limited company mid-year
- A large capital allowances claim reducing taxable profit
- Reduced trading due to illness or parental leave
The warning: if you reduce too far and the actual liability turns out higher, HMRC charges interest from the original due date, and can add a penalty if the reduction was made carelessly or deliberately. Reduce to a realistic figure, not an optimistic one.
A budgeting system that actually works
- Open a separate tax reserve account. Not a pot inside your current account — a genuinely separate account you never spend from.
- Sweep a fixed percentage of every payment received. For most sole traders on modest profits, 25–30% covers Income Tax and Class 4 NIC. Higher-rate earners should use 40–45%.
- Add the payment-on-account uplift in year one. In the first profitable year, sweep an extra 50% of your expected liability across the year so January does not double up.
- Reforecast in month nine. By month nine you know roughly where profits will land. Adjust the sweep percentage rather than discovering the gap in January.
- File early, pay late. Filing your return in May or June tells you the exact January number seven months ahead. The payment deadline does not move because you filed early.
Directors: the dividend timing lever
Dividends taken in one tax year land in that year's Self Assessment. If a dividend in late March would push you into the higher rate band, taking it in early April instead moves the tax and the resulting payment on account into the following cycle — a full twelve months of extra cash retention. This only works if the company has distributable reserves and the paperwork (board minute and dividend voucher) is dated correctly.
What happens if you cannot pay
Contact HMRC before the deadline and ask about a Time to Pay arrangement. Self-serve arrangements are available online for many Self Assessment debts. Interest still accrues, but you avoid the 5% late payment penalties at 30 days, 6 months and 12 months.
The bottom line
Payments on account are not an extra tax — they are a timing problem. Treat them as a scheduled, known outflow rather than a surprise, and the January deadline becomes an administrative date rather than a cash-flow crisis.