Methodology

Every calculator on this site includes its formula, worked examples and sources. This page collects the underlying conventions.

UK figures used

• Income tax 2026/27: Personal allowance £12,570; basic rate 20% to £50,270; higher rate 40% to £125,140; additional rate 45% above. Personal allowance tapers above £100,000.
• Class 1 NIC 2026/27: 8% between £12,570 and £50,270; 2% above.
• VAT: Standard 20%; reduced 5%; zero 0%; exempt.
• SDLT (England/NI): 0/5/10/12% bands at £250k/925k/1.5m thresholds. FTB relief 0% to £425k. Second-home surcharge +5%.
• ISA allowance: £20,000/yr; LISA £4,000/yr (counts toward overall ISA); Junior ISA £9,000/yr.
• Pension allowance: £60,000/yr; tapered above £260k income, £10k floor.
• State Pension: 35 NI qualifying years for full rate (~£230/wk illustrative).
• Stamp duty (Scotland LBTT, Wales LTT): separate bands — see dedicated calculators.
• Inflation: ONS CPI (or CPIH where specified). Use current published series.

Limitations

Calculators show illustrative results. They do not model: Scottish income tax bands, student loan repayments, child benefit clawback, marriage allowance, multiple-source income complexities, capital allowances, or non-standard tax codes. Always check personal figures with a qualified accountant or tax adviser for material decisions.

Editorial review

Calculations are reviewed in-house by a business analyst against current UK published data. See the editorial reviewer page.