If you choose rollover relief:

Last updated 24 February 2020

you disregard any capital gain or capital loss made under the demerger, and
your new interests in the demerged entity are acquired on the date of the demerger; however if a proportion of your original interests were acquired before 20 September 1985 (pre-CGT), the same proportion of your new interests in the demerged entity are treated as pre-CGT assets.

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