Bulletin Q&A article, published 2-5-23:
If you are late for Mass, is there some critical point in the liturgy required to meet your Mass obligation? The Confiteor? The gospel?
The Church requires that we attend Mass on Sundays and Holy Days of Obligation. Failure to do so is a grave matter and is considered a mortal sin if the person has knowledge of the requirement and still intentionally misses Mass without a valid reason. It is intended that Catholics attend the entire Mass. The General Instruction of the Roman Missal (GIRM) gives us a good reason: