15.—(1) Subject to subsection (2), any limit for the time being determined by a council under section 13, or applicable to it under section 14, shall be treated for the purposes of this Part as increased by the amount of any payment which—
(a)is due to the council in the period to which the limit relates, but
(b)has not yet been received by it.
(2) In the case of a limit determined under section 13, or set under section 14(2), subsection (1) shall not apply to any payment whose delayed receipt was taken into account in arriving at the limit.