Methodology

How each calculation works — figures verified for 2026/27 on 14 June 2026.

• Income tax — Personal Allowance £12,570 with the £100k–£125,140 taper (the “60% trap”); England/Wales and separate Scottish bands.
• National Insurance — Class 1 at 8% between the Primary Threshold and Upper Earnings Limit, 2% above; nil over State Pension age.
• Pension — salary sacrifice, net pay and relief-at-source are modelled separately because each is taxed differently.
• Student loans — one undergraduate plan (9%) plus optional Postgraduate (6%); undergraduate plans do not double-deduct.
• Mortgage — standard amortisation, with a fix-rate then revert/SVR two-phase model and ERC netting on overpayments.
• Stamp duty — SDLT, LBTT and LTT including the +5% / 8% surcharges and the separate Welsh higher-rate table.

Sources

• Income tax rates & Personal Allowance
• Scottish income tax 2026/27
• Employer rates & NI thresholds 2026/27
• Student loan deduction tables 2026/27
• Stamp Duty Land Tax
• Land and Buildings Transaction Tax (Scotland)
• Land Transaction Tax (Wales)

Estimates only — not financial advice.