Hundred SummersThe ISA bridge: can you get from here to your pension?
Retire before your pension unlocks and there is a gap only accessible money can cross: ISAs, taxable savings, cash. This calculator tests your bridge with the Hundred Summers app's real projection (pensions locked until the statutory access age, ISA drawn tax-free, income tax charged properly once the pension opens), and finds the smallest accessible pot that funds every year. Your figures never leave your browser.
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Worked example
Computed when this page was built by the same engine that runs the calculator above, so the figures below and the live tool can never disagree. Change any input above to see your own.
| Inputs | |
|---|---|
| Retire at | 48 |
| Spending a year | £28,000 |
| ISA / taxable pot | £200,000 |
| Pension pot (locked until 57) | £400,000 |
| Growth | 5.0% |
| Results | |
|---|---|
| Years to bridge before the pension unlocks | 7 |
| Does the plan work now | No |
| ISA pot the bridge needs | £310,000 |
| Gap | £110,000 |
The next question
What can my pension pay after that? →Pension drawdown calculator
Or answer it with everything else: the full Hundred Summers plan connects your pay, pensions, savings, property, tax and spending year by year, and stress-tests them across 500 simulated market histories.
Read the guide
- FIRE in the UK: what the American playbook misses →The 25× rule and savings-rate maths transfer; the mechanics don't. The pension access age bridge, ISA-vs-pension sequencing, UK tax on the way out, and where Coast and Barista FI fit: the honest UK version.
The constraint that shapes FIRE in the UK
Pension contributions get the best tax treatment in UK saving, and a lock that makes them useless for the years that define early retirement. The bridge inverts normal planning logic: for the bridge years, what matters isn't tax efficiency but accessibility, so early retirees deliberately fund ISAs past the point a pure tax optimiser would. The balance point depends on your retirement age: each year earlier adds a year of spending to the bridge AND removes a year of contributions and growth.
Run the numbers both ways: this page finds the accessible pot your date needs, and the when-can-I-retire calculator finds the earliest date your pots allow. The engine locks pensions at today's statutory 55: rising to 57 in April 2028, so treat a post-2028 plan as needing two more bridge years (the conservative reading). A market crash early in a bridge is sequence risk at its sharpest; the full Hundred Summers plan stress-tests your bridge through thousands of simulated markets and every historical sequence since 1928, with your real accounts and spending phases.