ISA access
Shows the projected value of investing the monthly amount directly into an ISA.
Tax wrapper decision tool
ISA vs Pension Calculator
Compare ISA flexibility with pension tax efficiency. Use the same take-home monthly amount and see what it could become inside an ISA or a pension; including salary sacrifice scenarios.
2026/27 UK rules reviewedTax relief modelled
Pension uplift
Estimates how tax relief or salary sacrifice can increase the gross amount invested.
After-tax comparison
Compares the ISA value with an estimated pension value after retirement tax.
Your numbers
The pension estimate assumes 25% of the pension pot can be taken tax-free and the remaining 75% is taxed at the retirement tax rate you choose. The ISA side assumes tax-free growth and access under current ISA rules.
ISA vs pension result
What this means
Enter your figures to compare the two routes.
Save or share this scenario
The page URL captures the figures you entered, so you can come back to the same ISA vs pension comparison later.
Same monthly cost, different wrapper
This table keeps the same take-home monthly amount and estimates how much gets invested through different routes.
| Route | Monthly cost | Estimated gross invested monthly | Projected pot | After-tax estimate | Access |
|---|
Year-by-year projection
A simple view of how the ISA and after-tax pension estimate build over time.
| Year | Age | ISA value | Pension after-tax estimate | Difference |
|---|
Tax and official tools
This tool already shows the pension after an assumed retirement tax rate, alongside the gross pot, while the ISA is treated as tax-free. Set the retirement tax rate to match your own situation, because your real rate depends on your other income at the time.
Sources used for this calculator:
Where to open each
An ISA is opened through an investment platform; a pension through a workplace scheme or a personal SIPP. The Knowledge Hub covers choosing an ISA platform and what to look for in a SIPP provider.
Assumptions and review date
Last reviewed: 19 May 2026. The calculator uses 2026/27 UK Income Tax, National Insurance, ISA and pension allowance assumptions for England, Wales and Northern Ireland.
It simplifies pension tax relief and salary sacrifice so the trade-off is understandable. It does not model Scottish tax bands, student loans, child benefit, provider fees, investment charges, scheme rules, tapered annual allowance calculations in full, or future tax changes.
How to use this calculator
The useful answer is not simply “pension” or “ISA”. The wrapper has to fit the job.
Pension often has a tax advantage
If the money is genuinely for retirement, tax relief or salary sacrifice can give the pension a head start before investment growth even begins.
ISA often has an access advantage
An ISA can be used before pension access age. That flexibility can be valuable for house deposits, career breaks, emergencies or earlier financial independence.
The split can matter more than the headline result
Many households need both: pension for retirement efficiency, ISA for optionality before retirement.
Useful next reads
These guides explain the decisions behind the numbers.
ISA vs pension: which should come first?
A practical explanation of flexibility, tax relief and access age.
ISA vs pension by tax band
Why the pension benefit can look different for basic-rate and higher-rate taxpayers.
Salary Sacrifice Calculator
Go deeper on the take-home pay cost of pension salary sacrifice.