(7)Nothing in this section shall be deemed to prevent the owner or charterer of a ship from claiming before the expiry of the assessment year relevant to the previous year in which the date of departure of the ship from the Indian port falls, that an assessment be made of his total income of the previous year and the tax payable on the basis thereof be determined in accordance with the other provisions of this Act, and if he so claims, any payment made under this section in respect of the passengers, livestock, mail or goods shipped at Indian ports during that previous year shall be treated as a payment in advance of the tax leviable for that assessment year, and the difference between the sum so paid and the amount of tax found payable by him on such assessment shall be paid by him or refunded to him, as the case may be.