Under what circumstances is it OK to omit saying either the Nicene Creed or the Apostles’ Creed during Mass?
This may help.
Thus the Creed may not normally be omitted on any Sunday Mass except as indicated below.
During the Easter Vigil and on Easter Sunday (but not on other Sundays of Easter Season), the renewal of baptismal promises and sprinkling with holy water replaces the Creed.
This is to emphasize the traditional connection of Easter Sunday with baptism and because the profession of faith is included in the baptismal promises.
Likewise, whenever baptism or confirmation is celebrated during Mass the profession of faith is omitted because the baptismal promises are either made or renewed during the rite.
The text of the Creed is usually that of the so-called Nicene Creed. According to the new Latin missal the Apostles’ Creed may be used during Lent, Easter and at Masses for Children. Some countries have received permission to use the Apostles’ Creed every Sunday.
The rite of sprinkling with holy water at Easter should not be confused with the similar rite of blessing and sprinkling of holy water which may replace the penitential rite and the “Lord, have mercy” at the beginning of most Masses with a congregation.
Sometimes liturgy guides for rites that occur during Mass will provide for the creed to be omitted. I don’t have an exhaustive list of such rites and I question whether there will ever be an exhaustive list.
But if the creed is permitted to be omitted on a Sunday, it is almost certainly because there is a renewal of baptismal vows or some other statement of faith and/or commitment by some or all of those who are attending that Mass.
And of course, sometimes, priests forget the Creed. It happens, especially because the Creed is not required for weekday Masses. But the Creed should never be intentionally omitted for Sunday Masses.
From the 2010 General Introduction to the Roman Missal:
“68. The Creed is to be sung or said by the Priest together with the people on Sundays and Solemnities. It may be said also at particular celebrations of a more solemn character.”
The Roman Missal’s Order of Mass, n. 19, allows either the Nicene or Apostles Creed at any Mass.
The Creed is optional when there are the Scrutinies, (prayers for the elect who are to be baptised a few weeks later.) From the book Rite of Christian Initiation of Adults: “… then, if required, the profession of faith is said. But for pastoral reasons these general intercessions and the profession of faith may be omitted.” (RCIA, n. 143, 157, 164 edition for Australia and England, n. 156, 170, 177 in the editon for the USA.).
The usual time for the Scrutinies is the Third, Fourth and Fifth Sundays of Lent. But it can be done at other times during the year, except Solemnities. (USA RCIA, n. 146, Australia RCIA n. 133).
At the Easter Vigil there is a renewal of baptismal promises, instead of the Creed.
The Creed is not said if there is a baptism in the Mass. (Rite of Baptism for Children, n. 29, The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 374).
And if there is a confirmation at Mass, from the Rite of Confirmation (Rite of Confirmation, n. 31. The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 492).
Nor if there is an ordination of a deacon, priest or bishop in the Mass, from the rite of “Ordination of Deacons, Priests and Bishops” (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, pages 28, 39, 66).
Nor if there is a consecration to a life of virginity in the Mass: (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, page 161, 177).
Nor if there is a rite of religious profession in the Mass,
for a temporary profession by a man: (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, page 213).
the same for a perpetual profession by a man, n. 52(b), page 221.
same if a man renews his vows, n. 83(b), page 233.
same for a women, temporary profession, 25(b), page 252.
same for a women, perpetual profession, 57(b), page 258.
same for a women, renewal of vows, 90(b), page 272.
Nor if there is a blessing of an abbot (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, page 304.
Same for the blessing of an abbess, n. 10, page 314.