Q1: If you’re late for Mass on Sunday, how late is too late?  As a child I was told you can’t miss the Gospel.  Later in life I heard you can’t miss the Offertory.
If you do miss the Gospel/Offertory, are you bound to stay for the next Mass?  Or just the part of the next Mass that you had missed?  What do you do if the Mass you were late for was the last Mass? –Timothy

Q2:  I have a parishioner who comes to daily Mass just in time for Holy Communion. I have asked why she doesn’t attend the entire Mass. She said she tries to get up earlier but just can’t.
I then informed her that according to the Church’s teaching, we are not supposed to receive Holy Communion if we miss the Gospel Reading….  If you are going to come to Mass, the Church teaches you are to be here for the entire liturgy.
​Can you help me​ with where it states in Canon Law about the rules of receiving Holy Communion in this instance?  I was hoping you could help me because I cannot find the exact paragraph. –Father M.
A: What does canon law say in response to every single one of these questions?  Absolutely nothing.  There isn’t a single mention of these issues in the Code of Canon Law, which explains why Father M. couldn’t “find the exact paragraph.”
That doesn’t mean, however, that it’s impossible to answer them.  Catholic moral theology can easily be applied here, which is one reason why the code doesn’t need to address the situation.  There are other good reasons why canon law is silent on the question of arriving late to Mass, which we’ll look at in a moment.
As we saw recently in “Which Mass Fulfills My Sunday Obligation?” canon 1247 tells us what we Catholics already know: on Sundays and holydays of obligation we are obliged to attend Mass.  The logical assumption is, therefore, that if Sunday Mass begins at (let’s say) 9:30 AM, we should arrive before 9:30 so we can be present at the whole Mass.
But as we all know, real-life doesn’t always work out like that.  For a million different reasons (more on this later), we might find ourselves walking in the church door at 9:35 or even 10 AM.  What are we supposed to do then?  It’s only reasonable for Catholics to assume that there’s some rule about this—like those supposed “rules” Timothy mentioned, about arriving before the Gospel or the Offertory.  In reality, no such rules exist.
Before you object to the Church’s failure to establish any rules, however, think about this: what would happen if the Catholic Church officially told the faithful that (for example) “so long as you arrive at Mass on Sunday or a holy day of obligation before the Gospel, you fulfill your obligation”?  The fallout that would quickly occur from such a declaration should be easy to envision.  Countless Catholics who heretofore have carefully made a point of getting to church before Sunday Mass begins would now conclude that there’s no need to do so, since getting there a few minutes late is sufficient.  Many people would wrongly decide that since it’s okay to miss the parts of Mass that take place before the Gospel, that means that elements like the Confiteor and the Gloria aren’t all that important—otherwise, why would the Church have said that we can arrive after these prayers have finished?
Soon enough, priests would find that at the time when Mass is scheduled to begin, the church is virtually empty, with most worshippers straggling in during the readings (distracting everyone in the process).  Some priests might react by waiting a few minutes to begin the Mass—but when parishioners figured this out, they’d react by arriving even later.  Eventually, the scheduled times for Masses would be meaningless!
What’s worse, those Catholics who were already trying vainly to get to Mass on time, yet still arriving a few minutes late, would now be emboldened to take their time.  Aiming to walk in the door right before the Gospel, they might end up getting there during the recitation of the Creed instead.
In short, setting any rules about arriving late for Mass would create a “slippery slope,” causing far more problems than it would solve.  We saw a comparable situation in “Can a Priest Ever Reveal What is Said in Confession? (Part II),” when discussing the reasons why the Church has made no official exceptions to the confessor’s strict obligation to maintain the sacramental seal.  Once a rule is no longer absolute, there’s no going back.  So when the Church tells us that we need to get to Mass on Sundays and holydays of obligations, it means just that.
Still, as already mentioned, countless Catholics do, for one reason or another, arrive at Mass after it has already begun—and they would appreciate some direction!  Ironically, that sentence contains a key phrase (“for one reason or another”) which is almost always overlooked in these discussions.  Why are they late?  What is the reason for their failure to arrive before Mass begins?  This is a critical point, because this is where moral theology comes into play.
The undeniable fact is, sometimes things happen which we genuinely could not have foreseen and cannot control, causing us to get to Mass after it’s started.  The car breaks down along the way; the baby vomits all over Mommy right when they’re heading out the door, requiring her to rush back inside and change her clothes; a multi-car crash closes the main road and obliges everyone to take a longer, roundabout route; you’re a doctor and en route to Mass you stop to help because you see a person has collapsed on the sidewalk; today the bus we normally take never came.  If we sincerely make our best effort to arrive at church on time, and something truly unexpected happens which causes us to be late, any competent theologian will tell you that we can’t be held morally responsible.  Lawyers will invariably say the same thing in the legal sphere, and for the same reasons: if you had no way of knowing that X would happen, and you really couldn’t do anything about it, then as a general rule you would not be liable.  Thus “punishing” people who are late to Mass for reasons like these makes no sense–and as we saw in “How Can You Tell a Real Law From an Illegal Decree?” sound laws must, by definition, be reasonable.
Of course there are two sides to this coin.  If we hit the snooze button on the alarm clock, or dawdle at home to check our messages before heading off to church, or otherwise take our sweet time getting to Mass … then the blame for arriving late lies squarely with us.  It’s tempting to try to deflect responsibility (“but we have kids!” is a very popular excuse, as if we didn’t know in advance that we have to get up earlier and/or prod them more insistently in order to be ready to leave for Mass on time).  An obvious rule-of-thumb is that once we figure out what time we have to wake up/leave the house in order to arrive punctually—making reasonable allowance for random things to happen along the way that might slow us down—then we shouldn’t wake up/leave the house any later than that.  It’s frighteningly easy to find Catholics who are late for Mass week after week, for the same reasons, which of course they ought by now to be able to foresee.  (And it’s amazing that when they’re going on vacation, these same people somehow always manage to arrive at the airport on time for their flight.)
Once we look at a case of late-arrival-to-Sunday-Mass through this lens, we frequently discover that what (if anything) is needed to rectify it can instantly become clear.  If you aren’t at fault, there is no reason to punish yourself; if you are to blame, then you naturally should make amends.  That’s why if you now look back at Timothy’s questions, it should be evident that the answer to all of them is “it depends.”
Common sense would dictate that if, through no fault of our own, we arrive so late that we’ve missed most of the Mass, we should attend another one.  This can largely become a judgment-call.  Devotion and love for God prompt many Catholics to stay for all or part of the next Mass because they want to—which is lovely and absolutely to be encouraged, but doesn’t constitute a “rule.”
Note that thus far we’ve been talking about arriving late on days when Mass is obligatory.  Attending Mass on ordinary weekdays is not required at all, although of course, it is laudatory to do so.  So if you’re late to a weekday Mass, even if you are entirely to blame, what’s the consequence?  There isn’t one.  It may understandably be frustrating for a priest like Father M. to see a parishioner straggle into church late for daily Mass day after day; but strictly speaking, she isn’t doing anything legally wrong.  After all, which is preferable: arriving late to daily Mass, or not attending daily Mass at all?
As both our questioners indicate, there is a common misperception that arriving late to Mass for any reason merits some sort of penalty.  But as we’ve just seen, this is bad theology—since you shouldn’t be punished if you haven’t actually committed a fault.  In particular, the notion that “we are not supposed to receive Holy Communion” if (for whatever reason) we’re late for Mass has no sound basis in Catholic sacramental theology whatsoever.  We’ve seen in various articles in the past (such as “Can a Baby be Baptized During Lent?” “Can a Priest Refuse to Hear Your Confession if He Knows You?” and “Can We be Required to Wear Masks at Mass?”) that canon 843.1 states clearly that the faithful cannot be denied the sacraments if they (1) ask for them at an opportune time, (2) are properly disposed, and (3) are not barred by law from receiving them.  A concrete example may serve to illustrate how canon 843.1 applies in this case.

Imagine that you normally attend early Mass on Sundays after working the night-shift at the hospital, and ordinarily, you arrive punctually with no problem—but this week some unusual emergency arose which prevented you from leaving work on time, thus making you late for Mass.  You are prepared to receive Our Lord in the Eucharist with devotion (so you are “properly disposed”), you aren’t under excommunication or some other sanction (i.e., there’s no reason why you would be “barred by law from receiving” Communion), and so you approach the priest at the point during the Mass when he distributes the Eucharist to the faithful (an “opportune time”).  Under such circumstances, there are absolutely no grounds, theologically or canonically, for denying you Holy Communion—even if you were late for Mass.  Father M.’s notion about “the Church’s teaching” is sheer fantasy.
All this being said, there are situations where refraining from receiving Holy Communion, and arriving late to Mass, are indeed logically connected.  It’s sad but true that some Catholics routinely saunter into church a good 30-40 minutes late, and once they sit down they immediately begin chatting or playing with their phones, making no effort to follow the Mass (or what’s left of it).  Such people obviously have no intention to attend Mass in order to show Almighty God the reverence that is due Him—in fact, it’s often difficult to understand why they bother to come to church at all.  While we can’t get into their minds and hearts to see what is actually happening there, their outward demeanor gives every indication that they are not “properly disposed” to receive the Eucharist, as per canon 843.1—and so they shouldn’t.
In this specific kind of case, arriving late for Mass is just one of many symptoms demonstrating an overall lack of faith and reverence.  But asserting that Catholics like these “came to Mass late” and “shouldn’t receive Communion” is a far cry from making a blanket assertion that lateness and refraining from Communion always go together.  They don’t.
So what can we take away from all this?  First and foremost, we’re supposed to do everything we reasonably can to get to Sunday Mass on time—period.  If we don’t make the appropriate effort and then we arrive late, we are to blame and need to do something to make it up to God (depending on how late we are, the best thing might be to attend another Mass).  If we do take every reasonable precaution and allow enough time to get to church before Mass begins, but something genuinely unforeseeable happens that makes us late, then morally we are not responsible for that.  While we might decide to make it up to God by staying for all or part of another Mass—assuming of course that there is one!—strictly speaking we can consider ourselves not morally bound to do that.
As for receiving Holy Communion, there is no automatic connection between doing so and arriving on time for Mass; if we are properly disposed to receive Our Lord, then we should.  Any priest who tried to withhold the Eucharist from somebody merely because he arrived late and for no other attendant reasons would unquestionably be violating that person’s right to receive the sacraments.
By now it should be clear that the Church didn’t make a mistake by failing to provide any official rules regarding our prompt arrival at Sunday Mass.  We are supposed to do all in our power to ensure that we get there on time—always aware that sometimes unexpected things can happen, over which we have no control and for which we cannot be blamed.

Source: Canon law made easy