UK tax tool
Self-Assessment Helper
A hedged estimate of your 2026/27 Self Assessment outcome from employment, side income, dividends and savings.
Estimated refund ~£14
Confidence: 60%Based on the figures provided. This is a simplified estimate and does not include Class 2 / 4 NIC, capital gains, or payments on account.
- Total tax estimated
- £5,486
- PAYE collected
- £5,500
- Marginal rate band
- 20%
- Adjusted non-savings income
- £40,000
- Tax on dividends
- £0
- Tax on savings
- £0
Always confirm via your HMRC Self Assessment account or a qualified accountant before filing.
What a result looks like
Sample: £40k salary, £5,500 PAYE, £8k freelance, £1k dividends. Estimated to owe ~£1,750.
What we check
- Combined non-savings income.
- PA taper above £100k.
- Dividend allowance £500.
- PSA £1,000 / £500 / £0.
- Higher-rate pension relief.
When to use this tool
- Year-end planning.
- Quarterly side-hustle health check.
- Budgeting for the January 31 bill.
What the result bands mean
Refund expected
PAYE may have over-collected.
Small bill
Possibly under £500. Check savings / dividend timing.
Larger bill
Worth setting money aside ahead of January 31.
Common mistakes
- Confusing turnover with profit.
- Forgetting the £1,000 trading or property allowance.
- Adding pension net instead of gross (we want gross).
Worked example
Employment £40k, PAYE £5,500. Side gig £8k profit. Dividends £1,000.
Non-savings: £48k - PA £12,570 = £35,430 x 20% = £7,086. PAYE covered £5,500. Owed on side income: ~£1,586.
Dividends: £500 free + £500 x 8.75% = £44. Total bill ≈ £1,630.
Frequently asked questions
Do I need to file Self Assessment?
Common triggers: self-employment over £1,000, untaxed income over £2,500, dividends over £10,000, income over £150,000, child benefit at higher income.
Does this calculate Class 2 / 4 NIC?
Not in this version. Adds may be needed for self-employed profit.
What about payments on account?
Not modelled. HMRC may also bill you upfront for the next tax year.
Do you handle capital gains?
No - those need a separate computation.
What about higher-rate pension relief?
We approximate it by extending your basic rate band by the gross contribution you enter.
Sources
- HMRC: Self Assessment manual.
- HMRC: Income Tax 2026/27 rates and allowances.
- HMRC: Personal Savings Allowance and dividend allowance.
Last verified: 2026-05-03.
Disclaimer: Simplified estimate only. Not a substitute for filing via HMRC or speaking to a qualified accountant.