Idaho Code § 28-22-105
Whenever a check, as defined in section 28-3-104, Idaho Code, has been dishonored by nonacceptance or nonpayment and has not been paid within fifteen (15) days and after the holder of such check sends such notice of dishonor as provided in section 28-22-106, Idaho Code, to the drawer, then if the check does not provide for the payment of interest, or collection costs and attorney's fees, the drawer of such check shall also be liable for payment of interest at the rate of twelve percent (12%) per annum from the date of dishonor and cost of collection not to exceed twenty dollars ($20.00) or the face amount of the check, whichever is the lesser; provided however, that if the holder of the dishonored check has the right to collect a set fee under a written agreement or has notified the drawer by a posted notice at the point of sale that the drawer will be required to pay a set collection fee if the check is dishonored, the holder is not required to give the notice of dishonor as provided in section 28-22-106, Idaho Code, and may assess a collection cost of the notice amount regardless of the size of the check, but the set fee may not exceed twenty dollars ($20.00). In addition, in the event of court action on the check, the court, after such notice and the expiration of said fifteen (15) days, shall award reasonable attorney's fees as part of the damages payable to the holder of the check. No attorney's fees may be awarded to a collection agency in a proceeding pursuant to section 1-2301A, Idaho Code. The provisions of this section shall not apply to any check which has been dishonored by reason of any justifiable stop payment order.
Idaho Code § 28-22-105