(1)A WRA assessment—
(a)may be made only in the two cases specified in subsections (2) and (3), and
(b)may not be made in the circumstances specified in subsection (4).
(2)The first case is where the situation mentioned in section 54 or 55 was brought about carelessly or deliberately by—
(a)the taxpayer,
(b)a person acting on the taxpayer’s behalf, or
(c)a person who was a partner in the same partnership as the taxpayer.
(3)The second case is—
(a)where WRA has ceased to be entitled to issue a notice of enquiry into a tax return, or has completed its enquiries into a tax return, and
(b)at the time when it ceased to be so entitled or completed those enquiries, it could not reasonably have been expected to be aware of the situation mentioned in section 54 or 55 on the basis of information made available to it before that time.
(4)No WRA assessment may be made if—
(a)the situation mentioned in section 54 or 55 is attributable to a mistake in the tax return as to the basis on which the devolved tax liability ought to have been calculated, and
(b)the mistake occurred because the tax return was made on the basis prevailing, or in accordance with the practice generally prevailing, at the time it was made.