The failure to file a tax return penalty under section 231-39(b)(l), HRS, shall not be imposed on any return filed on or before the extended due date if these conditions are met. However, if the stated conditions are not met, the automatic extension shall be deemed invalid and penalties and interest shall be assessed on the amount of tax owed as if no automatic extension had been granted (i.e., the computation of penalties under section 231-39(b) (1), HRS, and interest under section 231-39(b)(4), HRS, shall relate back to the due date prescribed by the statute).
Haw. Code R. § 18-235-98