Scope and limitations.

Tax computation scope

• Tax Owed: The process calculates and reports gains, losses, the Annual Exempt Amount (AEA), and net chargeable gains. It does not calculate final tax payable or Capital Gains Tax (CGT), as this depends on your personal Income Tax band and other circumstances.
• Mid-Year Rate Changes (e.g. 2024–25): The AEA is automatically allocated to gains in the higher-rate period first. Because the calculator cannot see income or gains outside your uploaded dataset (e.g. property sales, crypto or other broker accounts), this default split is a tax-efficient starting point rather than bespoke advice.
• Connected Person Losses ('Clogged Losses'): Losses from sales to connected persons (TCGA92 s18) can only offset gains made against the same person. The calculator does not restrict or track clogged losses.
• User-Reported Losses (LOSS rows): Losses entered via LOSS rows are accepted without validation and marked as user-reported in exports. You must ensure claims are valid and submitted to HMRC within four years (TCGA92 s16(2A)).
• External Exemptions & Gains: The calculator grants your full remaining AEA to the uploaded dataset. It cannot account for exemption amounts already consumed by external disposals (e.g. property, crypto, or other taxable disposals).
• Tax Residence: Assumes full UK tax residence. Split-year treatment, temporary non-residence rules, and remittance-basis claims are not supported.
• Exempt Assets: Gilts, Qualifying Corporate Bonds (QCBs), and ISA/SIPP holdings are not automatically filtered out. Remove exempt instruments from your file before uploading.
• SA108 Boxes 17.0 to 17.4 (2025–26 onwards): The 2025–26 Capital Gains Summary adds boxes 17.0 to 17.4 to the "Other property, assets and gains" section, for amounts claimed under the foreign income and gains (FIG) regime, disposals of non-residential land and buildings, and disposals where Business Asset Disposal Relief (BADR) is claimed. The calculator does not fill these boxes. If any of them apply to you, work out and enter those amounts yourself.

Currency and data entry

• Instrument Identifiers: Stock codes/tickers must be entered consistently across all rows (letter case is normalised automatically). Ticker changes or differing identifiers for the same underlying asset will be treated as separate holdings.
• Multi-Broker Portfolios: Matching rules (Same-Day, 30-Day, Section 104 Pool and later purchases) apply across your entire upload. If you trade the same asset across multiple broker accounts, combine transactions into a single dataset before importing.
• Currency: Values are assumed to be in GBP unless specified. When non-GBP codes are provided, values convert using either your explicit exchange rate or via our daily foreign exchange reference rates on the transaction date.
• Exchange Rates:
• The default historical exchange rate dataset used by this calculator is provided by the European Central Bank (ECB), and is otherwise freely available on the ECB's website.
• Where the ECB does not provide a rate for a given date, such as a weekend, the calculator uses the most recent prior available rate.
• Where a cross-rate or the base currency is different from those provided by the ECB, rates may be calculated via triangulation or inversion, particularly for less common currency pairs or where GBP is not the base currency.
• The ECB explicitly disclaims all liability for the accuracy, completeness, or ongoing availability of its foreign exchange reference rates. They assume no responsibility for any economic loss, loss of profit, or indirect damages resulting from the use of their published rates.

Corporate actions and reorganisations

• Rights Issues (RIGHTS_SALE):
  • The calculator applies small-distribution treatment whenever proceeds do not exceed the Section 104 pool cost. It does not verify HMRC’s 5% or £3,000 de minimis thresholds (CG57835); you must confirm eligibility manually.
  • Where proceeds exceed pool cost, the transaction represents a full part-disposal (TCGA92 s122(1)) requiring market value inputs, which are not currently supported.
• Corporate Restructuring: Takeovers, mergers, share-for-share exchanges (TCGA92 s135), demergers, and mixed-consideration part-disposals are not supported.

Fund income (ERI, accumulation distributions, and equalisation)

• Pool Adjustments Only: ERI, NOTIONAL, and EQUALISATION entries apply strictly to the Section 104 pool (not Same-Day or 30-Day trades) to adjust your base cost and prevent double taxation.
• Fund Types: Use NOTIONAL for UK-domiciled accumulation funds and ERI for offshore reporting funds. Select the correct event type based on your fund documentation.
• Equalisation: Applied in aggregate across the Section 104 pool on the distribution date, rather than tracked per individual tranche purchase.
• Manual Income Entry: Fund income and equalisation figures cannot be derived automatically from share prices; enter these directly from your tax vouchers.
• Non-Reporting Offshore Funds: Under HMRC rules, gains realised on the disposal of non-reporting offshore funds are treated as Offshore Income Gains (OIGs) and are subject to Income Tax rather than Capital Gains Tax. Currently, these funds are not supported by the calculator, and should be removed from your data and reported separately.

Spouse and civil partner transfers

• No-Gain / No-Loss Rules: Applied unconditionally under TCGA92 s58. The calculator cannot verify marital status, cohabitation, or post-separation time limits.
• Acquiring Spouse Pools: Generated BUY rows for the receiving spouse must be combined with any existing holdings of that asset to ensure proper Section 104 pooling.
• Eligible Couple Rules: The couple must still be living together and not separated, and there are special rules which apply in the year of divorce, which is not supported by the calculator.

Employee Schemes and Venture Capital Reliefs:

• Employee share schemes, the Enterprise Investment Scheme (EIS), and the Seed Enterprise Investment Scheme (SEIS) are currently out of scope. The calculator does not apply the specific reliefs, deferrals, or alternative matching rules associated with these schemes.

Historical data and tax years

• 31 March 1982 Rebasing: (TCGA92 s35) Automatic rebasing is not performed. For shares acquired before 31 March 1982, enter a single BUY row dated 31/03/1982 using the 1982 market value.
• Pre-1965 Assets: Pre-1965 rules and LIFO matching are not supported. Assets acquired before 1965 join the Section 104 pool at 1982 values.
• Abolished Reliefs: Indexation Allowance (frozen 1998) and Taper Relief (abolished 2008) are not supported. Disposals on or before 5 April 2008 are rejected on import to prevent incorrect tax calculations.
• Supported Tax Years: Disposals occurring in tax years not built into the system are rejected at upload. Annual exemption tables are updated as new legislative limits are enacted.

This scope reflects the system as built and is updated regularly as new features are released. This tool does not provide tax advice; always verify calculations against your primary records before submitting a tax return.