Corporate Tax

(a) Black Ltd owns 100% of the ordinary share capital of White Ltd. The results of Black Ltd and White Ltd for the year ended 31 March 2024 are as follows:

Black Ltd White Ltd
£ £
Trading profit/(loss) 396,800 (351,300)
Property business profit 21,100 26,700
Capital loss – (17,200)
Qualifying charitable donations (4,400) (5,600)
As at 1 April 2023 Black Ltd had unused trading losses of £57,900, and unused capital losses of £12,600, whilst White Ltd had unused trading losses of £21,800.

Required:
Advise Black Ltd as to the maximum amount of group relief that can be claimed from White Ltd for the year ended 31 March 2024 in respect of its losses. Clearly identify any losses that cannot be surrendered by White Ltd as part of the group relief claim.
The group relief claim by Black Ltd is calculated after deducting brought forward trading losses and qualifying charitable donations.
½
The maximum potential claim by Black Ltd is therefore £355,600 (396,800 – 57,900 + 21,100 – 4,400).
1
White Ltd’s qualifying charitable donations of £5,600 cannot be surrendered as they can be fully relieved against the company’s property business profit of £26,700.
½
It is not possible to surrender capital losses as part of a group relief claim.
½
Brought forward losses can only be group relieved to the extent that they cannot be used against the surrendering company’s own total profits, so White Ltd cannot group relieve any of its brought forward trading loss of £21,800 as this could be relieved against its property profit of £26,700. Therefore, only current year trading losses can be group relieved, so the maximum potential surrender by White Ltd is £351,300.
1
The maximum group relief claim is therefore £351,300.

the above is the tutorial note given by the study hub.
My question is, Why can’t we transfer the remaining QCD of 700 after deducting property profit with bf trading loss and QCD in group relief claim, when partial deduction is allowed? The rule states we can’t claim both QCD and bf trading loss. Can you please provide me with an explanation for the reason?
Also In the capital gains group, we are able to offset current year capital losses, but not in a group relief claim. Please clarify why this is the case, as the company still holds over 50% ownership.