This is from the general instructions of the Roman Missal.
usccb.org/liturgy/current/GIRM.pdf
43. The faithful should stand from the beginning of the Entrance chant, or while the priest
approaches the altar, until the end of the Collect; for the *Alleluia *chant before the Gospel; while
the Gospel itself is proclaimed; during the Profession of Faith and the Prayer of the Faithful;
from the invitation, *Orate, fratres *(
Pray, brethren), before the prayer over the offerings until the
end of Mass, except at the places indicated below.
They should, however, sit while the readings before the Gospel and the responsorial Psalm are
proclaimed and for the homily and while the Preparation of the Gifts at the Offertory is taking
place; and, as circumstances allow, they may sit or kneel while the period of sacred silence after
Communion is observed.
In the dioceses of the United States of America, they should kneel beginning after the singing or
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recitation of the *Sanctus *until after the *Amen *of the Eucharistic Prayer, except when prevented on
occasion by reasons of health, lack of space, the large number of people present, or some other
good reason. Those who do not kneel ought to make a profound bow when the priest genuflects
after the consecration. The faithful kneel after the *Agnus Dei *unless the Diocesan Bishop
determines otherwise.53
With a view to a uniformity in gestures and postures during one and the same celebration, the
faithful should follow the directions which the deacon, lay minister, or priest gives according to
whatever is indicated in the Missal.
It does not say stand after communion.