390Treatment of interest as a loss for purposes of carry-forward and carry-back
Where—
(a)a payment of interest eligible for relief under section 353 is money wholly and exclusively laid out or expended for the purposes of a trade, profession or vocation the profits of which are chargeable to tax under Case I or II of Schedule D, and
(b)full effect cannot be given to such relief in respect of the payment by reason of a want or deficiency of income of the year of assessment in which the payment is made,
the amount unallowed may be carried forward to succeeding years of assessment as if it were a loss carried forward under section 385, or may be treated for the purposes of sections 388 and 389 as a loss sustained at the date of payment.