The regulated firm closest to the investments does not trust the capital gains data coming out of the platform. The accountant who puts the gain on the self-assessment return relies on the same figures, months later, without the trade history.
What the research found
The lang cat's State of the Advice Nation research found 39% of advice firms cite tax planning as a priority, with the same proportion reporting a sharp rise in clients seeking reassurance about tax and legislative uncertainty. Michael Edwards, managing director of Financial Software Limited, said firms are contacting the company because they are "frustrated with CGT reporting across platforms, viewing it as either lacking or inconsistent". Greg Moss, a chartered financial planner and founder of Eleven.2 Financial Planning, said in the same coverage that the information needed to report accurately "already sits with the platforms", and that piecing it together takes hours of manual reconciliation.
How the figures reach the accountant
The financial planner decides what to sell and when, for reasons that are about the portfolio: rebalancing after a run in one holding, raising cash for a withdrawal, using an annual exempt amount before 5 April. The accountant meets that decision later, as a line on a statement, and has to turn it into a computation with a date, a base cost and a matching rule.
By the time the January deadline is close, the client has forgotten which units were sold, the adviser has moved on to the current year, and the platform report becomes the source by default. The CGT question in a client's file covers who notices the exposure.
What a platform report leaves out
A platform can see what happened on its own system. It cannot see:
- Reinvested income on accumulation units. The income is retained in the fund and taxed as income when it arises, so it is added to allowable base cost. A report showing only the original cash invested overstates the gain.
- Equalisation on the first distribution after a purchase. That element is a return of capital and reduces base cost.
- Holdings of the same fund on another platform. Share matching rules operate across the client's whole holding, so a same-day or 30-day repurchase elsewhere changes what the disposal is matched against.
- In-specie transfers that arrived without acquisition history. Units moved in from a previous provider can land with a transfer date and no original cost.
- Share class switches and fund mergers, some of which are disposals and some of which are not.
Each of these moves the figure on the return.
The figures for one holding
Illustration, using made-up figures. A client's general investment account holds accumulation units bought eight years ago for £40,000 and sold this year for £49,400. The platform tax pack reports a gain of £9,400: proceeds less the cash originally invested.
Over those eight years the fund retained and reinvested £5,200 of income, on which the client was taxed as it arose. Added to base cost, the allowable cost is £45,200 and the gain is £4,200.
For 2026 to 2027 the annual exempt amount is £3,000. On the platform figure £6,400 is taxable; on the corrected figure £1,200 is. For a higher-rate taxpayer the 24% rate applies:
- Platform figure: £6,400 × 24% = £1,536
- Corrected figure: £1,200 × 24% = £288
A difference of £1,248 on one holding, arising from base cost the platform had no way of knowing.
The rates used: the annual exempt amount is £3,000 (£1,500 for trusts), and gains from 6 April 2026 are taxed at 18% within the basic rate band and 24% above it, with the basic rate band at £37,700 for 2026 to 2027 (gov.uk, Capital Gains Tax rates and allowances).
How the two firms share the work
Where an accountant and a client's financial planner have a working relationship, the disposal history is requested once, in the spring, at transaction level, and the two firms agree which of them holds the base cost record. The financial planner has the trade rationale and the platform access. The accountant knows what a computation has to survive if HMRC asks. The reconciliation happens once, in April.
Where there is no such relationship the same work is done twice. The FCA's Financial Lives 2024 survey found that 8.6% of UK adults had taken regulated financial advice in the previous twelve months, and 13% of the self-employed.
The split of roles stays as it is while the data crosses it: the accountant computes and files, and the regulated firm advises on what to hold and when to sell. Who does what sets it out. Sharing a disposal history does not change it.
What is still uncertain
The FSL research measures what advisers want. There is no industry standard for CGT reporting in tax packs and no regulatory requirement to produce one, so improvement arrives platform by platform. The rise of CGT calculators to fourth in platform due diligence is the pressure that brings it.
The direction of CGT policy is open. The Budget has not been held, and speculation about capital gains is running ahead of anything announced. Nothing here depends on a rate change.
The split of responsibility between platform, adviser and accountant for the accuracy of a capital gains computation has not been formally allocated. In practice it falls to whoever signs the return. Gather the data early, from the party that holds it.
