Bond 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.

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.