January tax bill calculator: what you'll pay on 31 January 2027
Enter your 2025/26 profit, any CIS deducted and any payments on account already made. You'll get an estimate of the balancing payment and first payment on account due on 31 January 2027, the July 2027 payment, and whether a refund is likely.
How it works
- Income Tax on 2025/26 profit: £12,570 Personal Allowance, 20% to £50,270, 40% to £125,140 and 45% above, with the allowance reduced by £1 for every £2 over £100,000.
- Class 4 National Insurance: 6% of profit between £12,570 and £50,270, 2% above. Class 2 isn't due if profit is £6,845 or more.
- CIS deducted, tax paid through PAYE and payments on account already made are taken off. What's left is the balancing payment. If it's negative, a refund is likely.
- Payments on account for 2026/27 are each half of the 2025/26 bill after tax already paid. They aren't needed if that's under £1,000, or more than 80% was already paid.
Example: a CIS subbie
£36,000 labour with 20% CIS (£7,200) and £6,000 expenses gives £30,000 profit. Tax and Class 4 are £4,531.80, so the estimate is a £2,668.20 refund with no payments on account. See CIS refunds through Self Assessment.
This or the self-employed tax calculator?
This calculator is for last year's return (2025/26) and what's due on specific dates. To estimate this year's (2026/27) tax and take-home pay, and how much to set aside, use the self-employed tax calculator. For CIS only, use the CIS refund calculator.
Next steps
- Payments on account explained
- How to pay your bill, or Time to Pay if you can't
- All Self Assessment guides
Run a website? Embed this calculator on your site for free.
Free: The UK Contractor's Cheat Sheet 2026/27
CIS rates, overtime maths, tax dates, mileage, VAT and late payment, on 2 pages. Keep it on your phone or print it for the van.
Frequently asked questions
When is the January 2027 tax bill due?
By 31 January 2027, for the 2025/26 balancing payment and the first payment on account for 2026/27.
Does this include student loans?
No. Student loan repayments are added to the balancing payment separately.
Why does it show no payments on account?
Your bill after tax already paid is under £1,000, or more than 80% was already paid, for example through CIS.
Is this my exact bill?
No, it's an estimate. Your HMRC tax calculation is the final figure.
Sources
- Income Tax rates: previous tax years – GOV.UK
- Self-employed National Insurance rates – GOV.UK
- Rates and allowances: National Insurance contributions – GOV.UK
- Understand your Self Assessment tax bill: payments on account – GOV.UK
- What you must do as a CIS subcontractor – GOV.UK
This guide is general information, not legal, tax or financial advice. Rules and rates change, so check the linked GOV.UK pages for the current position.