Any taxpayer shall receive an extension of time to file the return required by this chapter to a day not later than six months from the day the return was originally due, if the taxpayer:
If the time for filing the return is extended at the request of the taxpayer, and the amount of tax due exceeds the reasonable estimate paid pursuant to subdivision (3), interest, but not penalty, shall be added to the difference at the same rate as provided for in § 10-59-6 from the time the return was originally due until the additional taxes due are paid.
SDCL 10-43-30.1