Idaho Code § 72-1354
If any amounts due under this chapter are not paid by any covered employer on or before the date on which they are due, such amounts shall bear penalty at the rate of four percent (4%) or twenty dollars ($20.00), whichever is the larger, for each month or fraction thereof until paid; provided, that in no case shall the penalty exceed the actual amounts due. The date of payment shall be deemed the date of actual receipt by the director, or if mailed, the date of mailing. Penalties collected pursuant to this section shall be paid into the state employment security administrative and reimbursement fund as established by section 72-1348, Idaho Code. At the discretion of the director, the department may compromise the amount of penalty collected pursuant to this section if the employer shows he had good cause for failing to timely pay contributions.
Idaho Code § 72-1354