If it is determined by the department, under regulations prescribed by it, that by reason of an individual being outside the United States, it is impossible or impractical to perform any one or more of the acts specified in this title, then in determining under this title whether the act was performed within the prescribed time, in respect of any liability for taxes, interest or penalties affected by the failure to perform the act within such time and in determining the amount of any credit or refund, including interest, affected by such failure, there shall be disregarded the period such person was thus unable to conform to the provisions of this title.