Hundred SummersBond gain calculator: top-slicing, done properly
Surrendering an investment bond triggers a chargeable event gain taxed under some of the strangest rules in UK tax: the gain divided by years held sets the rate for the whole gain, and onshore bonds carry a 20% credit for tax already paid inside. This calculator runs the Hundred Summers app's own top-slicing function. 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 | |
|---|---|
| Chargeable gain | £40,000 |
| Years held | 10 |
| Other taxable income | £30,000 |
| Bond type | Onshore |
| Results | |
|---|---|
| Tax due on the gain (onshore, after top-slicing) | £0 |
| Same gain in an offshore bond | £11,946 |
| Kept | £40,000 |
| Effective rate | 0.0% |
The next question
What capital gains tax would funds pay instead? →Capital gains tax 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
- Investment bonds and top-slicing: how a gain is taxed, and when it isn't →Onshore and offshore bonds, the 5% withdrawals that defer tax, chargeable events, and top-slicing relief: the rule that lets a ten-year gain be taxed as if spread over ten years, so a basic-rate taxpayer can pay nothing on an onshore gain.
Why bonds confuse everyone, including advisers
Investment bonds are life-insurance wrappers around funds, taxed under chargeable-event rules rather than capital gains tax: no CGT annual exemption, no dividend allowance; instead top-slicing, the 5% allowance, and segment assignment. The planning value is timing and ownership: gains crystallise when you choose, at whoever holds the segments then. Surrendering in a high-earning year instead of retirement, or in your name instead of a basic-rate spouse's, can double the bill this page computes.
Onshore bonds pay ~20% internally (the credit this calculator applies); offshore bonds grow gross but bear full rates on surrender: shown here conservatively at the full band cost before top-slicing relief. The full Hundred Summers plan holds bonds as a wrapper type and charges this same function on withdrawals in every projected year, so a surrender strategy can be tested inside your whole retirement plan rather than in isolation.