Exclusion of loss under tonnage tax limits pre-option shipping losses to set-off only against shipping income. Section 115VM confines pre-option losses attributable to a company's tonnage tax business to set-off under Section 72 against relevant shipping income while under the tonnage tax scheme, prohibits their set-off against non-shipping income for years beginning on or after the option date, and requires any necessary apportionment to be made on a reasonable basis.