Tax in the case of block assessment of search cases.

113.   The total undisclosed income of the block period, determined under section 158BC, shall be chargeable to tax at the rate of sixty per cent:

Provided that the tax chargeable under this section shall be increased by a surcharge, if any, levied by any Central Act and applicable in the assessment  year relevant to the previous year in which the search is initiated under section 132 or the requisition is made under section 132A.