(1) Where the Revenue Commissioners are satisfied that a Revenue estimate made under section 47 -

(a) is excessive, they may amend the amount so estimated by reducing it, or

(b) is insufficient, they may amend the amount so estimated by increasing it.

(2) Where subsection (1) applies, the Revenue Commissioners shall notify the person in respect of whom the Revenue estimate has been made that they have reduced or increased the Revenue estimate, as the case may be.