Capital Gains Supplementary Page
Totals for the cryptoassets and losses sections of your UK Self Assessment return, with the per-disposal computations HMRC requires you to attach.
- Taxable gain after exemption
- £12,810.00
- Losses carried forward
- £0.00
Chargeable at your CGT rate after the £3,000.00 Annual Exempt Amount.
£1,240.00 brought forward, all used against this year's gains.
Cryptoasset boxes 13.1–13.8
Page CG1 of the SA108 has a dedicated cryptoassets section for 2024/25 onwards. The figures below are transcribed exactly as they should appear on the form. Boxes 13.6–13.8 are left blank unless you used HMRC's Real Time CGT service.
any gains included in box 13.7 amounts must be included in this total
any losses included in box 13.7 amounts must be included in this total
Boxes 13.6–13.8 cannot be derived from your transaction history. Enter a three-letter code in 13.6 only if you are making a claim or election, and complete 13.7–13.8 only if you filed crypto disposals through HMRC's Real Time CGT service during the year. Amounts in 13.7 must also be included in 13.4 and 13.5, with the reference numbers in box 54.
HMRC's SA108 notes: you must enclose your computations, including details of each gain or loss, as well as filling in the boxes. Attachment A is that computation. The totals from SA108 carry into your SA100 to set your overall liability.
Losses and adjustments, boxes 45–48
Brought-forward losses can only reduce gains down to the Annual Exempt Amount (£3,000.00). Unused losses carry forward indefinitely. Prior-year losses of £1,240.00 were set against this year's gains, leaving nothing to carry forward.
Losses set against 2025-26 capital gains
2025-26 capital losses – other information
Losses must be claimed within four years of the end of the tax year in which they arose. Claiming them on this return preserves them for future years even when none are used now.
Basis of calculation and data sources
An agent or inspector reading the computation needs to know how each figure was produced. This page states the rules applied, the accounts included, and the reconciliation between the two ways of expressing the year's net position.
Each asset has one pool of aggregated cost. A disposal takes a proportionate share of the pool as its allowable cost.
Acquisitions on the day of disposal are matched first, before the pool is touched.
Acquisitions in the 30 days after a disposal are matched next, in date order. Matched disposals are marked in the Method column of Attachment A.
Trading and network fees attributable to acquisition or disposal are included in allowable costs. Transfers between your own accounts are not disposals.
GBP value at the transaction timestamp, using the spot price from the venue where available and a volume-weighted market rate otherwise.
Swaps are treated as a disposal at market value and an acquisition of the asset received.
Calculations run at full precision; presented figures are rounded to the penny, so column totals may differ by a penny from the sum of rows.
Staking and reward income is not a disposal and is reported on your SA100 instead.
The two lines agree, so the box figures and the per-disposal computation are consistent.