This section applies where—
The Board may, at any time before the end of the period of 3 years beginning with the time when the amount of the tax is finally determined, serve on any person to whom subsection (3) below applies a notice—
This subsection applies to any person who, at any time within the relevant period, was a trustee of the settlement, except that it does not apply to any such person if—
Any amount which a person is required to pay by a notice under this section may be recovered from him as if it were tax due and duly demanded of him; and he may recover any such amount paid by him from the migrating trustees.
A payment in pursuance of a notice under this section shall not be allowed as a deduction in computing any income, profits or losses for any tax purposes.
For the purposes of this section—