Qualifying ship definition: sets tonnage threshold, registration and certification requirements and specified vessel exclusions for tonnage income. A qualifying ship for tonnage-based income requires a minimum net tonnage, registration or a licence under the applicable shipping regime for the vessel, and a valid certificate indicating net tonnage; specified categories including vessels used primarily to provide goods or services normally provided on land, fishing vessels, factory ships, pleasure crafts, harbour and river ferries, offshore installations, and ships used as fishing vessels for over thirty days in a previous year are excluded.