If I attend two Masses in one day, can I receive Communion at both?
Code of Canon Law (CIC) allows for this: “A person who has already received the Most Holy Eucharist can receive it a second time on the same day only within the eucharistic celebration in which the person participates, without prejudice to the prescript of can. 921, §2.” (CIC 917)
Participation requires at least the normal level of participation of one attending Mass. (Canon 921, §2 deals with reception by those in danger of death.)