Investment Bonds Explained: Onshore, Offshore and the 5% Rule

An investment bond is technically a life assurance policy, but in practice it is used as a tax wrapper for investments. You pay in a lump sum (or sometimes top up over time), and the provider invests it across a range of funds you select. The "life cover" element is usually small — often 101% of the value — and exists mainly to give the contract its legal form.

The defining feature is how it is taxed. Investment bonds are not subject to UK capital gains tax on growth. Instead, they sit under a separate system of income tax rules that applies when a "chargeable event" occurs. Until then, growth rolls up either gross (offshore) or with a 20% tax already deducted inside the fund (onshore).

Bonds are usually written in segments — often a hundred or more — each of which can be cashed in independently. That segmenting matters because it gives you flexibility in how you take money out and how the tax falls.

Onshore bonds are issued by UK life companies. The fund inside pays UK corporation tax on income and gains, roughly equivalent to a 20% rate. When you cash in, basic-rate tax is treated as already paid — a "basic-rate credit". A basic-rate taxpayer has nothing further to pay; a higher-rate taxpayer pays an additional 20%; an additional-rate taxpayer pays an additional 25%.

Offshore bonds are issued from jurisdictions such as the Isle of Man, Dublin or the Channel Islands. The fund pays little or no tax in the jurisdiction where it is held — known as "gross roll-up" — so the whole gain rolls up untaxed until you withdraw. When you cash in, the full gain is taxed at your marginal income tax rate: 20%, 40% or 45%.

The headline trade-off is straightforward. Offshore bonds defer more tax during the investment period but give a larger tax bill at the point of withdrawal. Onshore bonds give a smaller tax bill at withdrawal but a smaller compounding benefit during the term. Neither is automatically better — it depends on your investment timescale, the funds available, and your expected tax rate in the year you withdraw.

Two further differences are worth noting. Offshore bonds are not covered by the UK Financial Services Compensation Scheme (FSCS), which can affect protection if the issuer fails. And charges on offshore bonds tend to be higher because they require specialist administration.

The most distinctive feature of an investment bond is the 5% allowance. You can withdraw up to 5% of your original investment each policy year for up to 20 years without triggering a chargeable event. Unused allowance carries forward, so if you take nothing in years one to four, you can take up to 25% in year five with no immediate tax charge.

It is important to understand what this allowance is and is not. The 5% is a tax deferral, not a tax exemption. The withdrawals are added to the calculation of the final chargeable event gain when the bond is eventually cashed in or you die — the tax is delayed, not removed.

For someone in or approaching retirement, the 5% allowance can be useful as a tax-light income source. A £200,000 bond, for example, would allow withdrawals of up to £10,000 a year for 20 years without triggering an immediate charge. That can be valuable for someone whose other income is already pressing against a tax band.

If you withdraw more than the cumulative 5% allowance, the excess is a chargeable event gain in that tax year.

A chargeable event is the moment the wrapper's tax shield ends and the underlying gain becomes taxable. Chargeable events include full surrender, the death of the last life assured, the bond reaching its maturity date, taking withdrawals above the cumulative 5% allowance, and — in some cases — assigning the bond for value.

The gain is calculated using a defined formula: broadly, the surrender value plus past withdrawals, less the original premium and any past chargeable event gains.

Where it gets useful is top-slicing relief. Without it, a large one-off gain crystallised in one tax year could push you into the higher- or additional-rate band purely because of the bond, even if your ordinary income is modest. Top-slicing relief recognises that the gain accrued over the years the bond was held. The relief works by:

• Dividing the gain by the number of complete years the bond was held to get the "slice".
• Calculating the additional tax on that slice based on your marginal rate.
• Multiplying that additional tax by the number of years held.

For a long-held bond, the relief can significantly reduce the actual tax payable on a chargeable event. The mechanics are complex; for any meaningful surrender, modelling the tax outcome with a tax adviser or financial planner is usually worthwhile.

For most UK investors, ISAs and pensions are the obvious starting point. The ISA allowance for 2026/27 is £20,000 and the pension annual allowance is £60,000 — both more tax-efficient than a bond for the typical investor.

An investment bond may become relevant where:

• You have used those allowances and have additional money to invest for the medium to long term.
• Your taxable income is high now but expected to fall in retirement, making deferral attractive.
• You are using trust structures for estate planning — bonds work well inside discretionary or other trusts because the chargeable event tax can fall on the settlor while alive, simplifying tax administration.
• You are an international or returning expat with offshore arrangements already in place.

Bonds are less commonly the right answer for someone whose ISA and pension allowances are not yet used, or for whom simplicity is more important than the additional flexibility. They also tend to carry higher charges than direct fund holdings, so the tax benefit needs to outweigh the cost.