UK Pension vs ISA Calculator 2026/27
Compare tax-efficient pension (SIPP) contributions vs a Stocks & Shares ISA using the same gross salary amount.
Last updated: June 2026
Investment assumptions
5.00 Thousand
Twenty
Five
Pension / SIPP
£5,000/yr gross · £100,000 contributed
Pot at end
£173,596
After tax (25% tax-free + taxed drawdown)
£147,557
Stocks & Shares ISA
£4,000/yr after tax · £80,000 contributed
Tax-free pot at end
£138,877
Pension advantage (after-tax vs ISA)
+£8,680
Negative means ISA wins under these assumptions (often when withdrawal tax equals contribution tax and growth is modest).
Data sources
Rates and thresholds on this page are based on official publications. Verify against the source for your specific circumstances.
- GOV.UK — Tax relief on pension contributions — verified 2026-06-01 · How pension tax relief works in the UK
- GOV.UK — Individual Savings Accounts (ISAs) — verified 2026-06-01 · ISA allowances and tax-free growth rules
Pension vs ISA — Key Differences
Pensions receive tax relief on contributions and grow free of UK tax, but most withdrawals are taxed (with 25% typically tax-free). ISAs are funded from post-tax income, yet all growth and withdrawals are tax-free with no lifetime allowance concerns.
This calculator uses the same gross amount from salary for both: the full amount goes into a pension, while the ISA receives the after-income-tax equivalent. At retirement, we apply your chosen drawdown tax rate to 75% of the pension pot.
Employer pension match, annual allowance limits, and National Insurance savings on salary sacrifice can make pensions even more attractive — those are not included in this simplified model.
Educational comparison only. Does not include annual allowance, lifetime allowance history, LISA rules, or personalised advice. Speak to a regulated financial adviser for your circumstances.