The Earned Income Credit (EIC) is a refundable tax credit that has a significant impact on United States revenue. It is also the source of a disproportionately large number of errors in tax returns in which a claim for it is made. This course briefly summarizes the earned income credit rules, examines the common errors committed when claiming the credit, discusses the EIC due diligence requirements imposed on professional tax return preparers, and identifies the sanctions to which preparers and their employers may be subject for a failure to meet expected due diligence requirements.