Tonnage tax scheme requires separate business treatment and distinct computation for qualifying shipping operations upon exercise of option.
An elective tonnage tax scheme treats qualifying shipping operations as a separate business requiring separate computation of profits; operation includes owned, chartered and partial charter arrangements. Tonnage income is computed under the Part's computation provision and deemed to be profits of business, with relevant shipping income not chargeable where the scheme applies. The regime is available only if the company exercises the statutory option; absent the option, general provisions apply.