Where does the same take-home pound go furthest?
Compare equal cost today, not unequal headline contributions. Provider relief, any higher-rate reclaim, National Insurance saving, employer matching and pension withdrawal tax are all visible.
Saved setupsNothing is saved automatically
Both options reduce today's take-home by £400 a month and grow at 5% for 25 years.
| Today's monthly ledger | ISA | Pension |
|---|---|---|
| Personal take-home cost | £400.00 | £400.00 |
| Paid to pension provider | — | £400.00 |
| Provider tax relief | — | +£100.00 |
| Employer contribution | — | +£0.00 |
| Total invested | £400.00 | £500.00 |
| New ISA input this year | £4,800 |
|---|---|
| New pension input this year | £6,000 |
| Normal minimum pension age from 2028 | 57 |
Planning rangeHow returns and withdrawal tax could change thisCompare lower, selected and higher assumptions.
The lower outcome reduces annual growth by 2 percentage points and adds 5 points to pension withdrawal tax. The higher outcome does the reverse. Everything else stays the same.
- Lower outcome3.0% growth · 25% withdrawal tax
- Pensionhigher after-tax value
- £2,772modelled difference
- Selected assumptions5.0% growth · 20% withdrawal tax
- Pensionhigher after-tax value
- £14,643modelled difference
- Higher outcome7.0% growth · 15% withdrawal tax
- Pensionhigher after-tax value
- £34,258modelled difference
This range is not a forecast. Returns vary, charges reduce outcomes, and future tax rules can change.
- Pension has the higher modelled valueThe difference is £14,643 after the withdrawal-tax assumption.
- Access is the central trade-offISA money remains accessible. Most pension money is locked until at least age 57 from April 2028, unless a protected age or exception applies.
- Check for an employer matchForgoing available matching is usually a large immediate loss before investment returns are considered.
A simplified defined-contribution comparison under 2026/27 rules, not investment or tax advice. It applies the enacted April 2029 salary-sacrifice NI change, but excludes charges, benefit interactions and unentered future tax changes.
How this calculation works
The Stocks and Shares ISA receives the monthly take-home budget. Relief at source separates your provider payment, the provider's basic-rate top-up and any further tax relief you reclaim. Salary sacrifice separates gross pay exchanged from income-tax and employee-NI savings, including the enacted NI limit from April 2029. Both wrappers use the same growth assumption; pension withdrawal tax is applied after the entered tax-free share.