The B&B rule confuses me a bit since disposals are matched with future acquisitions (done within 30 days). What happens to tax calculations (for each tax year) if the tax year ends in between the disposal and acquisition?


  1. Assume I bought 10 shares many many years ago (but after the introduction of Section 104)
  2. 5 days before the end of tax year A, i sell 5 shares
  3. tax year A ends; i happily fill in my tax form by matching the disposal of 5 shares in the previous step with the 10 shares in my Section 104 holding and (possibly) pay capital gains on that
  4. 5 days after the end of tax year A, now in tax year B, i buy 5 shares

According to the B&B rule, the disposal in step 2 now matches with the acquisition in step 4. So what now?

  • Have I retrospectively filled in my self-assessment incorrectly for tax year A and paid the wrong amount of capital gains tax?
  • What do I do now for tax year B?
  • What is the correct "status" of my "ledger"? Ie, what does my Section 104 holding pot look like? Which disposals/acquisitions matched with which?


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