Being late for Mass is not, in itself, sinful. What is sinful is not fulfilling Sunday/Holy Day Obligation. To fulfill your obligation, you must participate at Mass, arriving no later than before the Gospel and departing no earlier than the Prayer After Communion. If you arrive, say, at the Offertory, you may still receive Communion at that Mass provided you are otherwise disposed and have the intention of attending at least the portion of the Mass you were absent at another Mass later that day (no such obligation exists for a weekday Mass). Furthermore, the same scenarios which would excuse you from attending Mass entirely also excuse you for being late, so if you are late for the last Mass of the day for reasons that would have justified missing Mass entirely if they had persisted, you are excused and can receive Communion. If, however, you are late for the last Mass such that you do not fulfill your obligation through your own fault, or you refuse to attend another Mass after being too late to fulfill your obligation at an earlier Mass, you shall not present yourself for Communion.