Glossary

Checked against app build 2026-08-26-01-41 on 2026-08-26.

Every term the app and the UK rules use, defined once and linked to the page that goes further. Each entry has its own anchor, so you can link straight to a definition.

The tax terms

The words UK capital gains tax law uses, in the sense the legislation and HMRC use them.

Annual exempt amount (AEA)

The tax-free capital gains allowance, £3,000 a year since 2024 to 2025. Gains under it in a year owe no capital gains tax. The current year’s figure and how it interacts with other gains are in the CGT allowance tool.

Bed and breakfast rule

The nickname for the 30-day rule, selling and rebuying within 30 days matches the sale against the rebuy, see the UK rules. The bed and breakfast rule calculator dates the window for a disposal.

Cost basis

What you gave up to acquire units, purchase price plus allowable costs. Missing cost basis is the finding that protects you from overstated tax, see missing acquisitions.

Disposal

Any event tax law treats as you parting with an asset, a sale, a swap into another asset, spending, or gifting to anyone but your spouse or civil partner. The spouse exception has its own spouse transfers tool.

Matching

Deciding which acquisition a disposal is set against, same-day first, next 30 days second, the pool last.

Negligible value claim

A section 24(2) TCGA 1992 claim that an asset you still hold has become worthless, crystallising the loss without a sale. See the negligible value claims tool.

Pool, section 104

The running per-asset holding at average cost that absorbs everything not matched by the first two rules.

Proceeds

What a disposal brought in, in pounds, at the time it happened.

Tax year

6 April to 5 April, the UK’s year, every report is grouped by it.

The gains.tax terms

Words that mean something specific inside the app, and are worth knowing before you read a screen.

Confidence score

The app’s live grade of its own certainty about your figures, out of 100, explained in the confidence score.

Reconciliation

The work of making the workspace agree with reality, imports previewed, counts explained, flags answered, wallets balancing.

Session file

The complete workspace as one file, exports free at any size, reopens in the app anywhere, never locked.

Tax event

A row that matters to the computation. Files count rows, the engine counts tax events, the difference is shown at import, see the reconciliation count.

Working paper

The report showing every disposal with its rule, arithmetic and citation, the audit trail behind every other number.