After you file

Well I would have to imagine that there is an answer to it. They process all refunds on a first come first serve basis correct? But do they skip over EITC refunds? Or do they complete them and just hold sending refunds until the law allows?  If they just skip over them it seems to me like that would be an extraordinary amount of returns to review and approve in a short time. Because they do make the statement of it being usually being within 21 days still.