Idaho Code § 63-3041

If the taxpayer has paid more than the amount determined to be the correct amount of the tax, the excess shall be credited or refunded as provided in section 63-3072, Idaho Code, as amended. In the event a joint return has been filed and one (1) spouse dies prior to issuance of credit or refund, the credit or refund may be granted the surviving spouse. In the event a joint return has been filed by a couple separated after filing of the return, the credit or refund may be equally divided between such persons unless a joint claim has theretofore been properly executed.