1. Social Security Number (or Individual Taxpayer Identification Number)
2. Filing Status
3. The exact whole dollar amount of your refund
https://sa1.www4.irs.gov/irfof/lang/en/irfofgetstatus.jsp
CA return는 아래 사이트에서 refund status를 확인하실 수 있습니다.
https://webapp.ftb.ca.gov/refund/login.aspx?Lang=en-US