The Church’s Code of Canon Law (updated in 1983) allows the faithful to receive communion twice in the same day, provided they attend the Mass at which they receive the Eucharist. Thus an individual may receive Communion at a daily Mass, and again at a wedding, funeral or other ritual (see Canon 917).
Insisting an individual attend the Mass at which she or he receives Communion stresses the communal aspect of the Eucharist. At Mass, the Catechism of the Catholic Church teaches, “we already unite ourselves with the heavenly liturgy” (No. 1326). We also unite ourselves with other members of Christ’s Body. The rule also discourages overzealous or superstitious souls from wandering from church to church and taking part in no more of the Mass than the Communion rite.
Deacons who assist at more than two Masses must excuse themselves from receiving Communion after the second, but the law does not apply to the dying, and states, “The Christian faithful who are in danger of death, arising from any cause, are to be nourished by holy Communion in the form of viaticum. Even if they have received Communion in the same day [they] are strongly urged to receive again” (Canon 921).