Is missing Sunday Mass considered a mortal sin?


My wife and I were recently told that missing Sunday Mass was considered a mortal sin and required penance prior to participating in Holy Eucharist the following week by a friend of ours. Is this accurate? (If there is a grey area in responding to this question, could you explain how this act could be possibly considered either a venial or mortal sin depending on the circumstances?)

I searched for an explanation in the Catechism and could not find where this was defined. Maybe there is something in Cannon Law, I’m just not sure. I did find in section 1416 however, that communion in the Body and Blood forgives venial sins and preserves him from grave sins.

Thank you for your response in advance.


Missing Mass without a good reason is a grave matter. But keep in mind that mortal sin requires full knowledge and complete consent. The catechism states: “The Sunday Eucharist is the foundation and confirmation of all Christian practice. For this reason the faithful are obliged to participate in the Eucharist on days of obligation, unless excused for a serious reason (for example, illness, the care of infants) or dispensed by their own pastor. Those who deliberately fail in this obligation commit a grave sin.” (CCC 2181)

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