It is an act that, at the invitation of the priest celebrating the Mass, the whole congregation, after a brief pause for silence, carries out through a formula of general confession of sinfulness. It concludes with absolution by the priest, which, however, lacks the efficacy of the Sacrament of Penance.
Formulas of general confession
All: I confess to almighty God,</br> and to you, my brothers and sisters,</br> that I have sinned through my own fault,</br> in my thoughts and in my words,</br> in what I have done,</br> and in what I have failed to do;</br> and I ask blessed Mary, ever virgin,</br> all the angels and saints,</br> and you, my brothers and sisters,</br> to pray for me to the Lord, our God.</br>
- Formula B:
Priest: Lord, we have sinned against you: Lord, have mercy.</br> Congregation: Lord, have mercy.</br> Priest: Lord, show us your mercy and love.</br> Congregation: And grant us your salvation.</br>
- Formula C (said or sung by the deacon or priest, or sung by a cantor):
Minister: You were sent to heal the contrite (or a similar invocation): Lord, have mercy.</br> Congregation: Lord, have mercy.</br> Minister: You came to call sinners (or a similar invocation): Christ, have mercy.</br> Congregation: Christ, have mercy.</br> Minister: You plead for us at the right hand of the Father (or a similar invocation): Lord, have mercy.</br> Congregation: Lord, have mercy.</br>
Formula of absolution
In all cases, the formula of absaolution that follows is:
Priest: May almighty God have mercy on us, forgive us our sins, and bring us to everlasting life.</br> Congregation: Amen.
Place within the Introductory Rites
The Penitential Acts follows the entrance of the priest (ideally to the sound of the entrance antiphon or a hymn), and his greeting of the altar (which he kisses) and of the people (with a formula such as "The Lord be with you"). In turn it is followed by the Kyrie eleison (unless the third of the three formulas, which incorporates the Kyrie, has been chosen as the Penitential Act), the Gloria (if used), and the Collect, which concludes the Introductory Rites.
When certain celebrations are combined with Mass the Penitential Act, as well as other parts of the Introductory Rites, is omitted or performed in a different way. An example is the Mass of Ash Wednesday, in which the blessing and imposition of ashes, after the homily, replaces the Penitential Act at the beginning.