Self Assessment Tax Calculator UK 2025/26

Self assessment tax calculator UK 2025/26 — calculate income tax, NI Class 2/4, payment on account. Sole trader, landlor

Quick answer: Self-employed sole trader earning £40,000 profit in 2025/26: £5,486 income tax + £2,194 Class 4 NI + £179 Class 2 NI = £7,859 total. Plus 2 payments on account at 50% each (£3,929.50 each in Jan + Jul of next tax year).
Mustafa Bilgic
Reviewed by Mustafa Bilgic · UK Calculator Editor ·

Calculator

Self Assessment covers self-employed (sole traders), partners, landlords, dividend earners over £10k, high earners (£150k+), and anyone with untaxed income. This calculator estimates your full tax bill including income tax, Class 2 + Class 4 NI, and payment on account schedule.

How self assessment tax calculator works in 2025/26

What goes on a 2025/26 Self Assessment return:

  • Self-employed income — sole trader profit (Box 7-78 on SA103S/F)
  • Partnership share — your portion of partnership profits (SA104)
  • UK property rental — landlord income net of allowable expenses (SA105)
  • Dividends over £500 — UK and foreign (Box 8 on SA100)
  • Interest over £1,000 — bank/building society (Box 1 on SA100)
  • Foreign income — pensions, work, investments (SA106)
  • Capital gains — disposals of shares, property (SA108)
  • High Income Child Benefit Charge — if income £60k+ and receive child benefit

NI for self-employed 2025/26:

  • Class 2: £3.45/week (£179.40/year) — voluntary if profits under £6,725 small profits threshold; mandatory if above
  • Class 4: 6% on profits £12,570-£50,270, 2% above £50,270 (note: NOT 8% — Class 4 was reduced from 9% to 6% in 2024/25)

Payment dates:

  • 31 January — balance owed for 2024/25 + first payment on account for 2025/26 (50% of expected bill)
  • 31 July — second payment on account for 2025/26 (50% of expected bill)
  • 31 January next — balance for 2025/26 + first payment on account for 2026/27

Worked example: Sole trader £30k profit (no other income)

IT: PA £12,570; £17,430 × 20% = £3,486. Class 2 NI £179.40. Class 4 NI: £17,430 × 6% = £1,045.80. Total £4,711.20. Payment on account 2026/27: £2,355.60 each in Jan + Jul.

Gross: £30,000 → Take-home: £25,288.80/year (£2,107.40/month)

Worked example: Landlord £25k rental + £45k employment

Employment: PAYE handles £45k. Rental £25k taxed at marginal rate (40%): £10,000 income tax. Already used PA on employment. Property allowance not claimed (income > £1k). Net £15,000 from rental after tax.

Gross: £70,000 → Take-home: £50,000.00/year (£4,166.67/month)

Worked example: Side hustle £5k freelance + £40k employment

Employment: PAYE on £40k. Side hustle: trading allowance £1,000 → taxable freelance £4,000 at 20% = £800. Class 2 voluntary £179. Class 4 6% × £4,000 = £240. Total extra tax £1,219.

Gross: £45,000 → Take-home: £36,500.00/year (£3,041.67/month)

Frequently asked questions

Who has to file Self Assessment?
You must file if: self-employed earning £1,000+ (or under £1k but want to claim losses), partner in a partnership, landlord earning £2,500+ rental, dividend income £10k+, total income £150k+ (was £100k pre-2024), high-income child benefit charge applies, capital gains over allowance.
When is the deadline?
Online filing: 31 January following the tax year end. Paper filing: 31 October. So 2025/26 (ending 5 April 2026) deadline online = 31 January 2027. Penalties: £100 immediately, more after 3, 6, 12 months.
What's payment on account?
HMRC asks you to pre-pay 50% of your expected next year's tax bill on 31 January and another 50% on 31 July. Once filed, balancing payment makes up the difference. Doesn't apply if your previous year's bill was under £1,000 or 80% was paid via PAYE.
Can I reduce my payments on account?
Yes — file form SA303 if you expect this year's income to be lower. Be careful: if you reduce too much, HMRC charges interest on the underpayment from the original deadline. Reduce only if confident.
What's Making Tax Digital (MTD) for self-employment?
From April 2026, sole traders and landlords with income over £50k must use MTD-compatible software, file quarterly returns, and submit a year-end declaration. Income £30-50k joins April 2027. Below £30k stays on annual return for now.
Can I claim home office expenses?
Yes — simplified expenses £10-26/month based on hours, OR actual proportion of bills (electricity, gas, broadband, mortgage interest portion). Plus tools, mileage at 45p/mile (first 10k), professional subscriptions, training.
Do I have to register for VAT?
Mandatory if turnover exceeds £90,000 (2024 threshold) in any 12-month rolling period. Voluntary registration possible below — useful if your customers are VAT-registered (you reclaim input VAT on purchases). Consider Flat Rate Scheme for small businesses (16.5% LCT for service businesses).

Official UK Sources

Last reviewed: May 2026 against HMRC 2025/26 rates.

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