Pension vs ISA Calculator 2026/27
Pension contributions benefit from upfront tax relief -- a basic rate taxpayer investing £100 into a pension only parts with £80 from take-home pay. But pension withdrawals are taxed. ISAs offer no upfront relief but all withdrawals are completely tax-free. Which comes out ahead depends on your tax rate now versus your expected tax rate in retirement, how long you invest, and whether you need access before pension age. This calculator models both options from the same net take-home cost and shows the projected pot and net-of-tax value at retirement.
The pension vs ISA trade-off explained
The core difference is the timing of the tax advantage. A pension gives you relief upfront -- contributions are made before income tax, so more money goes in from the start. An ISA gives you relief at the end -- no tax on withdrawals, ever. Which is better depends entirely on your tax rate at contribution time versus your tax rate at withdrawal time.
When pension wins
If you pay higher rate tax now but expect to be a basic rate taxpayer in retirement, a pension is clearly more efficient. You get 40% relief going in but only pay 20% coming out. Even for basic rate taxpayers, the pension often wins because of the employer contribution -- effectively free money that you cannot get into an ISA.
When ISA wins
If you expect to pay the same or higher tax in retirement, or if you need flexibility to access money before age 57, an ISA may be preferable. ISAs also have no annual allowance restriction on how much of the pot you can draw tax-free -- there is no equivalent of the Lump Sum Allowance cap.
Frequently asked questions
For most people, pensions are more tax-efficient for long-term retirement saving because of upfront tax relief. A basic rate taxpayer investing £100 into a pension only costs £80 from take-home pay. A higher rate taxpayer saves even more. ISAs offer no upfront relief but all withdrawals are tax-free, which advantages those who expect higher tax rates in retirement or who want flexibility before pension age.
Yes. There is no rule against contributing to both in the same tax year. Many financial planners recommend maximising pension contributions first to capture employer contributions and tax relief, then using an ISA for additional savings. The ISA allowance is £20,000 per year in 2026/27.
The ISA allowance for 2026/27 is £20,000 per person per tax year. This can be split across cash ISA, stocks and shares ISA, innovative finance ISA, and Lifetime ISA (LISA sub-limit £4,000). Unused ISA allowance cannot be carried forward.
Pensions are typically more beneficial for higher rate taxpayers. A higher rate taxpayer receives 40% tax relief on contributions. If they later draw in retirement as a basic rate taxpayer, they have converted higher rate relief into basic rate tax on withdrawal, which is a significant advantage. However, this depends on your expected income in retirement.
Yes. ISA savings can be accessed at any time with no tax penalty. Pension savings cannot currently be accessed before age 55 (rising to 57 in April 2028) without incurring significant tax charges, except in cases of serious ill health. If you may need your savings before pension age, ISA flexibility is a meaningful advantage.
Disclaimer: This calculator provides estimates for guidance purposes only. Tax rules are complex and individual circumstances vary widely. Always consult a regulated financial adviser before making pension or investment decisions.