Bethany timely filed her 2001 1040 tax return and paid the $2,000 tax as shown on the return at the time of filing. The return was subsequently examined and Bethany signed an agreement form for the proposed changes on August 20, 2003. She paid the additional tax due of $5,000 on September 30, 2003. In 2004, Tiffany located missing records which she believes would make $3,000 of the additional assessment erroneous. Which of the following statements accurately states the date by which Bethany must file a claim for refund to get the $3,000 back?