John is a permanent member of the Irish Naval Service. In 2021, John spent 128 days at sea on board an Irish naval vessel. In 2022, John spent 73 days at sea on board an Irish naval vessel.
John can claim this tax credit for 2022 as he spent at least 80 days at sea in 2021. However, as John spent less than 80 days at sea in 2022, he cannot claim the credit for 2023.