This section applies where a person ("P") carrying on a ring fence trade who for a consideration disposes of, or of an interest in, any assets ("the old assets") declares, in P's return for the chargeable period in which the disposal takes place—
Until the declaration ceases to have effect, section 198A or 198B applies as if the acquisition had taken place and the person had made a claim under that section.
The declaration ceases to have effect as follows—
On the declaration ceasing to have effect in whole or in part, all necessary adjustments—
If—
on P making a claim, the declaration is to have effect as also a declaration under section 153A.
In this section "the relevant day" means—
Section 152(6), (10) and (11) apply for the purposes of this section as they apply for the purposes of section 152.