Self-Assessment Tax Estimator
Self-employed and director pay self-assessment in two payments on account, each 50% of last year's bill, plus a balancing payment.
Updated May 2026, using HMRC 2026/27 rates and current ONS / gov.uk figures.
Self-assessment isn't just last year's tax — HMRC also takes payments on account towards next year. If your bill was £5,000, you'll pay £5,000 in January PLUS £2,500 on account. Then £2,500 on account again in July. The calculator above estimates the basic tax + NI; below is how the payments-on-account rule works.
How it works. Estimates income tax + Class 4 NI for self-employed at 6%/2%. Real bill depends on allowable expenses, capital allowances, and personal circumstances.
Worked examples
First-year self-employed earning £40,000: tax + Class 4 NI ~£6,300. Payments on account from year 2: £3,150 in Jan + Jul of next year.
Director on £12,570 salary + £40,000 dividends: total tax ~£4,000. POA from next year: £2,000 in Jan + Jul.
Sources:
HMRC Self-Assessment
· retrieved 2026-05-12.
Frequently asked questions
What is a payment on account?
HMRC's way of getting tax in advance. Each payment on account is 50% of last year's tax bill, due 31 January and 31 July. They're credited against next year's bill.
Can I reduce my payment on account?
Yes, if you genuinely expect lower earnings — via SA303 or online. But if you reduce them and earnings turn out higher, HMRC charges interest on the shortfall.
When is the deadline?
Online self-assessment: 31 January after the end of the tax year (5 April). Paper: 31 October. Late filing: £100 fixed penalty plus daily/percentage penalties after 3 months.
Should I do my own self-assessment or use an accountant?
If you have only PAYE-equivalent income (employment + simple savings/dividends), it's often manageable. Self-employed, multiple income sources, property income, or company directors should usually use a qualified accountant or tax adviser — the cost typically pays for itself in claimed allowances.