Q. 1. I was told that if one arrives late at Holy Mass, he/she is not entitled to receive Holy Communion. So my question is, "At what point of the Mass when someone arrives after it has started, is it too late to receive Holy Communion?"
A. 1. I would like to point out that there is no right answer to your question. If I say it is allowed to arrive late up to a certain point of the Holy Mass, this will provide the less fervent souls with an excuse to arrive late.
Attending Holy Mass means accepting the Lord Jesus' invitation to participate in His great Banquet. It is like responding to a King's invitation to join him at a feast. Such an invitation means being there to eat a five course meal that includes the soup, the appetizer, the salad, the dinner or main entree, and the dessert. Would it be polite to arrive late? Would it be polite to tell the King that you do not care for the soup and/or the appetizer? Or would it be polite to skip the dessert and leave early? All of these behaviours would be rude.
To arrive late at Mass is not just a matter of fulfilling one's Sunday obligation, it is an act of love and respect for the Lord Jesus who is gathering His children to share in the great moment during the Holy Mass when He will become physically present among the faithful. Each and every part of the Holy Mass is important, inseparable from one another.
Prior to Vatican II, some theologians taught that arrival before the offertory was necessary to fulfill one's Sunday obligation. The Catholic Church no longer supports this teaching. Its emphasis is now on the overall unity of the Holy Mass.
If one has a valid reason for arriving late, such not being a regular habit, then the Lord may excuse him/her. This may be because of unexpected road conditions, a severe storm, waiting for a train to clear the tracks, etc... But if arriving late means arriving at Church after the consecration, in truth, one has not attended Holy Mass, should not receive the Sacrament of the Holy Eucharist, and if on a Sunday (and if it is possible), he/she should go to another Mass.
If you arrive late for Holy Mass, ask yourself with a sincere heart if you should receive Holy Communion? You be the judge of the matter before God. If sharing in the Lord's Banquet means something to you, then you should be there from the entrance procession at the beginning of the Holy Mass to the final dismissal at the end of the service.