What will you pay on 31 January?
Income Tax plus Class 4 National Insurance. Leave out capital gains and student loan repayments: they're never part of payments on account.
CIS, PAYE, or payments already made?
CIS deductions withheld by contractors, or PAYE tax on employment income for the same year.
If you paid instalments last January and July towards this bill, put their total here.
Due 31 January
£0.00
Type your bill above and the payments work themselves out.
Due 31 July
£0.00
Payments on account cover Income Tax and Class 4 National Insurance only. Anything owed for capital gains or student loans is added to the January balance on top of what's shown here.
How payments on account work
Once you owe £1,000 or more at Self Assessment, HMRC collects next year's tax in advance: two instalments, each half of this year's bill, due 31 January and 31 July. The instalments are worked out on the amount you owe after tax already taken at source, so CIS deductions and PAYE reduce them.
No instalments are due at all if either escape applies: the amount you owe after tax at source is under £1,000, or more than 80% of your year's tax was met at source. The calculator applies both tests.
The shock is the first year. Your full bill lands on 31 January, and the first instalment towards next year lands the same day: a £4,000 bill becomes £6,000 due at once, then £2,000 more in July. It's not extra tax, just next year's arriving early. The full mechanics, with the year-by-year table, are in payments on account, explained.
If you expect to earn less
You can ask HMRC to reduce your payments on account, online or by post on form SA303, telling them what you expect to owe. One warning attached: if you reduce them and the real bill comes in higher, HMRC charges interest on the difference. That's information straight from gov.uk, and whether reducing is sensible in your case is a judgement for you or your accountant.
Quick answers
Is the January payment extra tax?
No. It's next year's tax arriving early: your bill plus the first advance instalment, both due the same day. July takes the second instalment, and next January nets off what you've already paid.
What if my income drops next year?
Apply on SA303 to reduce the instalments to what you expect to owe. Reduce too far and interest applies on the shortfall.
Do CIS deductions change the amount?
Yes. Instalments are computed on your bill net of tax at source, and CIS counts. Over 80% met at source means no instalments at all.
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Know your January number all year
SoleTax keeps a running estimate of the tax to set aside as you earn, payments on account included, so 31 January is a date, not a surprise. 14 days free, no card needed.
Join the betaSources: gov.uk, understand your Self Assessment bill (payments on account, including reducing them on SA303) and HMRC's Self Assessment legal framework manual SALF303. Checked on 4 July 2026.