Iowa Code § 452A.51
The purpose of this subchapter is to provide an additional method of collecting fuel taxes from interstate motor vehicle operators commensurate with their operations on Iowa highways; and to permit the state department of transportation to suspend this collection as to transportation entering Iowa from any other state where it appears that Iowa highway fuel tax revenue and interstate highway transportation moving out of Iowa will not be unduly prejudiced thereby. Further, all motor vehicle operators from jurisdictions not participating in the international fuel tax agreement are required to comply with this chapter using the guidelines from the international fuel tax agreement for Iowa fuel tax compliance reporting purposes, penalty, interest, refunds, and credential display.
Iowa Code § 452A.51