The Calculator
This calculator applies statutory HMRC share identification rules matching disposals to acquisitions in order:
- Same day acquisitions (TCGA92/S105),
- Acquisitions within the following 30 days in chronological order, bed-and-breakfasting (TCGA92/S106A),
- Against the Section 104 holding using its pooled average cost (TCGA92/S104), and
- Finally, against later acquisitions, the earliest first, for any part of a sale bigger than the shares held (TCGA92/S105(2)).
Allowable dealing charges and Stamp Duty are factored into acquisition and disposal costs. Foreign exchange calculations are included, and crypto-level precision is maintained. Output figures are structured by UK tax year (6 April to 5 April), apply the relevant Annual Exempt Amount, and account for mid-year tax rate changes where applicable.
Privacy
Your transaction data is processed in memory and discarded once the response is sent. The transaction data itself is not written to disk, logged or shared. We retain only anonymised usage statistics, such as the number of rows and transaction types processed and the calculation timestamp, not the data itself. See the Privacy Policy.
Maintenance & Accuracy
Calculations for share matching, corporate actions, and fund distributions have been developed and tested against a variety of scenarios. Testing and development processes are used to identify and correct errors and improve consistency. We make reasonable efforts to maintain the service and its accuracy, but it is not an assured or guaranteed service. Tax legislation and HMRC guidance evolve over time, and updates are deployed as quickly as practical. See the scope page for supported transaction types, tax treatments, generalisations and known limitations.
Fair Use
To ensure consistent availability on shared infrastructure, standard and/or temporary limits apply to processing volume (rows per import and total calculations per user). This service is designed for interactive Web UI use and is not intended for automated API or bulk processing. If your dataset is large and exceeds standard limits, please get in touch for a customised solution.
Disclaimer
This tool is provided for informational purposes only and does not constitute formal tax, accounting, or legal advice. Results are based on the transaction data and other information supplied by the user. Always verify all figures in the output and underlying transaction data before using it for tax reporting purposes.
Refer to the following pages for input formatting for data preparation, worked examples for event type usage, and scope page for known limitations.