How do you use the annual Capital Gains Tax exemption efficiently?

01 Why an unused exemption is a real loss

The annual exempt amount is £3,000 of gains a year, free of tax, and it does not carry forward. A holding left untouched for a decade accumulates a single large gain, and only £3,000 of it is exempt in the year of sale — the other nine years' worth of exemption has expired.

Realising and reacquiring resets the base cost to the higher price, so future gains are measured from there. Done annually, that converts a large future taxable gain into a series of exempt ones.

The exemption has been reduced sharply in recent years, from a much higher figure, which makes using it every year more valuable rather than less. A smaller allowance wasted is still an allowance wasted.

One qualification is worth stating. Realising a gain deliberately makes sense where the base cost is materially below the value; on a holding barely in profit there is nothing to realise and the dealing costs are the only certain outcome. The exercise is about the holdings with the largest embedded gains, not about selling something every year for its own sake.

On the defaults above, the worked example shows £6,480. A single disposal at the end would be taxed £6,480; realising within the exemption each year costs £0.

Source: Capital Gains Tax allowances

02 The 30-day rule

Selling and immediately rebuying the same holding does not work. Share matching rules match a disposal against any acquisition of the same holding within the following 30 days, so the gain is not realised as intended and the base cost is unchanged.

Three routes get around it legitimately. Buy back after 30 days, accepting the market risk in between. Buy a similar but not identical fund — a different index tracker covering the same market. Or repurchase inside a wrapper, which is what a Bed and ISA does.

The wrapper route is the best of the three, because it realises the gain, resets the base cost and moves the holding somewhere it will never be taxed again.

Source: Tax when you sell shares

03 Two exemptions in a couple

Transfers between spouses and civil partners are made at no gain and no loss, so an asset can be moved to whichever partner has unused exemption before it is sold. That gives a household £6,000 of exempt gains a year rather than £3,000.

It also lets the disposal happen in the hands of the partner with the lower Capital Gains Tax rate — 18% within the basic-rate band against 24% above it — which is a further saving on gains beyond the exemption.

The transfer has to be an outright gift. The asset becomes theirs, in a divorce and in their estate, and that is the genuine cost of the technique rather than a formality.

Source: Capital Gains Tax rates

04 Reporting, and when you have to

Gains within the exemption generally need no report where you are not otherwise in Self Assessment and proceeds do not exceed the reporting threshold. Beyond that, gains are reported through Self Assessment or, for UK residential property, through a separate return within 60 days of completion.

Records matter more than the reporting. The base cost of a holding acquired over years of monthly contributions is a calculation, and platforms do not always retain it after a transfer. Keeping annual statements is what makes a disposal computable a decade later.

Losses are worth recording too: they can be set against gains in the same year and carried forward indefinitely, but only if claimed within four years of the end of the tax year in which they arose.

It is also worth knowing what the exemption does not cover. Your main home is generally exempt through private residence relief and does not touch the annual amount at all, and gains inside an ISA or pension are outside the tax entirely. The annual exempt amount is a rule about unwrapped investments and second properties, which is a much narrower set of assets than people assume.

Source: Capital Gains Tax

05 The annual routine

Each January, look at the unwrapped holdings and identify £3,000 of gain to realise, choosing the holding whose base cost is lowest relative to its value. Sell it, and either repurchase inside an ISA subscription or buy a similar fund outside one.

Where a spouse has unused exemption, transfer part of the holding first so both are used. Where losses exist, decide whether to crystallise them in the same year or carry them forward — losses set against gains within the exemption are wasted, so timing matters.

Then record the new base cost. That figure is what makes next year's calculation simple, and it is the thing nobody writes down.

Source: Capital Gains Manual