Hi JGregory,
Please refer to the following guidance as this explains the rules around allowable losses and the, rare, circumstances in which they can be carried back. It is unlikely these will apply in this case.
CG15800 - Losses: allowable losses
The gains on which the provisional roll-over relief claim was made occurred in 2021 to 2022 and if the losses realised were in a future year it is unlikely the losses will be able to be utilised against this gain. Roll-over relief provides 3 years to re-invest gains in to the business but does not alter the year in which the gain occurred.
Thank you.