Just as our Creed states, we “believe in one baptism for the forgiveness of sins.”  The Catholic Church takes this mandate very seriously and recognizes all Christian baptisms performed in the Trinitarian form:  A person is either submerged or has water poured over their head three times while the words “I baptize you in the name of the Father, and of the Son, and of the Holy Spirit” are recited by the presiding minister.  The Church takes great care in determining if a person has ever been baptized before conferring the Sacrament. 
 
The Rite of Christian Initiation of Adults (RCIA) is the formation for people seeking baptism and membership in the Catholic Church (a Catechumen).  After preparation they are formally invited to the Easter Sacraments and receive Baptism, Confirmation and Eucharist, typically at the Easter Vigil.
 
Many men and women seek membership who have already been baptized in another Christian faith using the Trinitarian form.  We acknowledge them as already one with us in Christ and, after preparation, they are invited to make a profession of faith and are then Confirmed and invited to share with us in the Eucharist.  The RCIA includes an adapted rite for these “Candidates” and they become members of the Catholic faith along with the newly baptized at the Easter Vigil.  However, Candidates can be accepted into the faith anytime throughout the year following suitable preparation.