(1) Upon receipt of an application for refund of fuel tax, the department of transportation has 120 working days after receiving the claim to approve or reject it.

(2) After approval of the claim, the department will process the refund.

(3) After rejection of the claim, the department may, after investigation, require the claimant to file an amended statement before action is taken.   If the taxpayer submits an amended claim, the claim is reasonable, and the taxpayer has furnished substantial proof, the department in its discretion may accept the amended claim.

(4) A taxpayer may, of their own initiative, file an amended claim.   If the claim is reasonable and the taxpayer has furnished substantial proof, the department, in its discretion, may accept the claim.