A verified claim for an income tax credit or refund may be submitted on an amended return (AR1100CTX) or on the taxpayer's letterhead as set forth in 1. 26-18-507(a). Upon request by the Department, it shall be the burden of the taxpayer to prove that all claimed prior income tax payments that are reflected on an amended return or verified claim for credit or refund were made. The Department will accept legible copies of the front and back of canceled checks as proof of prior payments. Where the taxpayer paid the tax at issue via Electronic Funds Transfer ("EFT"), documentation from the taxpayer's bank will be necessary to establish proof of payment.
1.26 Ark. Code R. 18-306(i)(1)