Can you receive Communion in mortal sin?

No. If you're aware of having committed a mortal sin, the Church asks you to go to Confession before you receive Communion (CCC 1385; Code of Canon Law, can. 916). There is one narrow exception, for a grave reason when Confession is truly impossible. Until you can confess, keep going to Mass, stay in your pew at Communion, and get to Confession as soon as you can.

What does the Church teach?

The Catechism says it simply: "Anyone aware of having sinned mortally must not receive communion without having received absolution in the sacrament of penance" (CCC 1415). Church law says the same thing: a person conscious of grave sin is not to receive the body of the Lord without previous sacramental confession (can. 916).

This holds even when you're deeply sorry (CCC 1457). Sorrow that comes from love of God reconciles you with him before you reach the confessional, as long as you mean to confess. But the ordinary order is still Confession first, then Communion. We explain how that kind of sorrow works in perfect and imperfect contrition.

Why does mortal sin keep you from Communion?

Communion is the closest union with Christ there is. Receiving him means saying yes to him with your whole life. Mortal sin is a choice that turns a person away from God and destroys charity in the heart (CCC 1855). Receiving Communion in that state would be saying yes with your body while your will is still saying no.

St. Paul warned the Christians in Corinth about this, in words the Catechism quotes (CCC 1385): "Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of profaning the body and blood of the Lord. Let a man examine himself, and so eat of the bread and drink of the cup. For any one who eats and drinks without discerning the body eats and drinks judgment upon himself" (1 Corinthians 11:27-29).

The Eucharist and Confession also do different things. Communion strengthens charity and wipes away venial sins, but it isn't meant for forgiving mortal sins. That belongs to the sacrament of Reconciliation (CCC 1395).

What counts as being in mortal sin?

The rule is for people who are aware of a grave sin. A sin is mortal when three things come together: grave matter, full knowledge, and deliberate consent (CCC 1857). If you didn't know something was seriously wrong, or you weren't really free, it may not have been a mortal sin at all. We go through the three conditions in what is a mortal sin?

If you honestly can't tell, ask a priest. And if you tend to worry about sin more than most, ask your confessor for a simple rule about Communion and then follow it. A rule confessors often give scrupulous penitents is to receive unless they are certain they sinned gravely. That's pastoral counsel for an over-anxious conscience, so let your own confessor tell you whether it fits you. Our page on scrupulosity has more help for that kind of worry.

Do venial sins keep you from Communion?

No. Venial sins, like impatience, small lies or distraction in prayer, don't bar you from Communion. Receiving Communion itself wipes them away and strengthens you against mortal sin (CCC 1394-1395). The penitential act at the start of Mass is a good moment to tell God you're sorry for them, and then you go up and receive.

Is there any exception?

One, and it's narrow. Canon 916 allows a person conscious of grave sin to receive Communion only when both of these are true: there is a grave reason to receive, and there is no opportunity to confess. In that case the person must make an act of perfect contrition, which includes the resolution to confess as soon as possible. The Catechism names the same two conditions (CCC 1457).

Both conditions have to be real. The example often given is a priest who has to celebrate Mass for his people and has no way to reach a confessor beforehand. For most lay people, feeling awkward about staying in the pew isn't a grave reason. And "no opportunity" means truly none: very often you can ask a priest before Mass to hear your confession, and many will. If you think the exception might apply to you, ask a priest rather than deciding alone.

What should I do at Mass if I'm in mortal sin?

1. Keep going to Mass. The Sunday obligation is to take part in Mass, not to receive Communion every time. Being there matters, and God is at work in you even from the pew.
2. Stay in your pew at Communion. Let people pass you. No one is keeping track. People stay seated for all sorts of reasons: they ate within the hour, they aren't Catholic, they're waiting to go to Confession. In many parishes you can also go forward with your arms crossed over your chest to receive a blessing instead. Customs vary, so follow what your parish does.
3. Make a spiritual communion. Tell Jesus, in your own words, that you want him and you're sorry. Something as simple as "Lord, I can't receive you today, but I want you. Give me true sorrow and bring me back soon." Then pray an Act of Contrition.
4. Go to Confession soon. Check your parish's Confession times, or call and ask for an appointment. Once you've been absolved, you can receive at the next Mass, even the same day.

What if I already received Communion in mortal sin?

Then confess that too. Receiving Communion while knowingly in mortal sin is a grave sin in itself. The Catechism calls treating a sacrament unworthily sacrilege, and says it is grave especially when it concerns the Eucharist (CCC 2120). It is also forgivable like any other sin. Say it simply: "I received Communion while I was in mortal sin, twice." The priest won't be shocked. He has heard it before, and he'll be glad you came.

If you received without realizing a sin was mortal, or because you had honestly forgotten a sin in your last Confession, you didn't commit that sin. A mortal sin forgotten in good faith was forgiven with the rest, and you simply mention it next time (see I forgot a sin in confession).

If it's been a long time

Maybe you've stayed in the pew for months or years and the gap feels too wide. It isn't. One good Confession brings you back to the altar. Tell the priest it's been a while. Name the mortal sins you can remember, with a rough idea of how often, and trust him to help you with the rest. You don't need a perfect memory of every year. Our guide to going back to Confession after years walks you through it step by step.