In the case where a return is filed concerning inheritance tax on property acquired by inheritance or universal legacy, or in the case where reassessment or determination is made concerning inheritance tax on that property, if all or part of the property acquired by that inheritance or universal legacy has not yet been divided by the co-heirs or universal legatees, the taxable value for the property that has not been divided is to be calculated on the assumption that each co-heir or universal legatee has acquired that property in accordance with the share of inheritance under the provisions of the Civil Code (excluding Article 904-2 (Amount of Contribution to the Estate)) or the proportion of the universal legacy; provided, however, that if the property is subsequently divided and the taxable value relating to the property acquired by the co-heir or universal legatee through that division comes to differ from the taxable value calculated in accordance with that share of inheritance or proportion of universal legacy, this does not preclude the person liable for tax from filing a return or making a request for reassessment prescribed in Article 32, paragraph (1), or the district director from making reassessment or determination, on the basis of the taxable value relating to the property acquired through that division.