Donaldson R F UK Self Assessment Tax Calculator
Bring together trading profit, other income and dividends to estimate your 2026/27 Self Assessment bill, your balancing payment and whether you'll owe Payments on Account.
Trading income
Other income this tax year
How it is worked out
Trading profit is turnover minus either your actual expenses or the £1,000 trading allowance, whichever you choose (use whichever gives you the lower profit). Your trading profit, other income and dividends are combined, your Personal Allowance is worked out (reduced by £1 for every £2 of total income over £100,000), and Income Tax is charged on non-dividend income first, with dividends stacked on top — dividends always use the England/Wales/Northern Ireland band limits to decide which dividend rate applies, even in Scotland, because dividend tax is not devolved.
Class 2 National Insurance is treated as already paid once profits reach £7,105 (no cash payment in this estimate either way — below the threshold it's voluntary). Class 4 is 6% of profits between £12,570 and £50,270, and 2% above. Student loan repayments are 9% of combined income above your plan's threshold (6% above £21,000 for a postgraduate loan).
Payments on Account are required unless this year's Income Tax + Class 4 NI is under £1,000, or you already had 80% or more of it deducted at source. Each one is half of that figure, due 31 January (alongside the balancing payment for the year just ended) and 31 July.
Sources: GOV.UK: Tax-free allowances on property and trading income, Self-employed National Insurance rates, Tax on dividends, Payments on Account, Self Assessment deadlines. Checked 7 October 2026.
Need just one part of this? Try the National Insurance Calculator, Dividend Tax Calculator, or UK Tax Year Dates.