Tonnage tax reserve requirement: companies must set aside a mandated portion of shipping book profits for ship acquisition and restricted use. Tonnage tax companies must credit a Tonnage Tax Reserve Account with a mandated minimum portion of book profit from qualifying shipping activities each year; shortfalls due to losses may be carried forward to the next year. Reserve funds must be used within eight years primarily to acquire a new qualifying ship or inland vessel or, until acquisition, for operating qualifying ships subject to restrictions on dividends, remittances and creation of foreign assets. Misapplication, failure to utilise, or disposal within three years triggers proportionate taxation under the general tax provisions, and two consecutive years of non creation terminates scheme eligibility.