Clarification of same-day and B&B rules for shares

I am trying to clarify some details about the same-day rule and bed & breakfasting rule for CGT calculations. Suppose that I performed the following transactions with shares in a given company on 1st Jan 2020: a) earned £450 from the sale of 50 shares at 09:00; b) earned £550 from the sale of 50 shares at 12:00. If I am correctly interpreting the description of the same-day rule given in CG51560 then, for CGT purposes, I should treat these as a single sale of 100 shares, with net proceeds of £1000. Suppose that I also: c) bought 25 shares on that date. According to CG51560, 25 of the shares that I sold on 1st Jan should be identified with these 25 purchased shares, and the remaining 75 sold shares "will be identified in the normal way". Question 1: Does the "normal way" mean that these 75 shares should be identified with the section 104 holding, regardless of whether or not I purchased more shares between 2nd and 31st Jan 2020? Or, as HS284 suggests, should I first identify as many of these 75 shares as possible with shares purchased between 2nd and 31st Jan (under the bed & breakfasting rule), and then identify the surplus with the section 104 holding? Question 2: Assuming that I should follow the bed & breakfasting rule, the pages that I've cited do not specify the time at which the 30-day window ends for the 1st Jan sales. Since these sales should be treated as a single sale, perhaps it's just a question of picking a time for this single sale and adding 30 * 24 hours = 720 hours to it. What time should I assume for the single sale? Market open time? The time of the first or second sale? Market close time? Some other time? This question may seem pedantic, but: 1) I'm writing software that does CGT calculations, so I need a more precise rule; and 2) I need answers that apply to CGT calculations for cryptocurrencies too, which can be traded 24/7. Suppose that the rest of my January 2020 transactions, for the company in question, were as follows: d) bought 50 shares on 8th Jan 2020; e) sold 25 shares on 15th Jan 2020; f) bought 50 shares on 22nd Jan 2020. I now have 75 unidentified shares that I sold on 1st Jan, and 25 unidentified shares that I sold on 15th Jan. A Twitter customer support agent mentioned a "first in, first out" rule for bed & breakfasting (https://twitter.com/HMRCcustomers/status/1746908222265369017). So if the bed & breakfasting rule applies to the 75 unidentified shares, then I take it that this FIFO rule means that: * 50 of these shares should be identified with my 8th Jan purchase; * the remaining 25 should be identified with half of my 22nd Jan purchase; * my 15th Jan sale should be identified with the other half of my 22nd Jan purchase. Question 3: Is this correct? Question 4: Where is this FIFO rule stated in the Capital Gains manual? When I asked question 4 on Twitter, customer support referred me to CG13370 and CG51500, but those pages say nothing about this rule.

Hi,

Guidance is available at:

HS284 Shares and Capital Gains Tax (2023): How to identify the shares disposed of

CG51560 - Share identification rules for capital gains tax from 6.4.2008: the “same day” and “bed and breakfast” identification rules

Thank you.

I cited both of those documents in my post; my questions are about things that they do not properly explain. I'm just going to assume the following answers to my first three questions: Q1. "the normal way" means I should apply the B&B rule first, and then identify the rest with my section 104 holding. Q2. Time should be ignored, meaning e.g. that all purchases on 31st Jan are within the B&B window for 1st Jan sales, regardless of the times of those sales. Q3. Yes. I hope someone will tell me if this is incorrect. If not, I guess I'll only find out if HMRC ever decides to verify my CGT calculations.

Hi,
As you state the same day and bed & breakfast identification rules can be found at CG51560. the 'same day' takes priority then 'bed & breakfast'
The normal way will depend on if the transactions form part of the original Section 104 or if a new holding is required.  
The time of the acquisition or disposal will not matter so long as it is on the same day.  
More information on FIFO found at CG51565.  
Regarding Self Assessment, HMRC takes the approach of process now check later.
Thankyou.