Sections 473 through 486 give three pages of information on the Church’s approach to receiving baptized Christians into full Communion. These sections, along with the rites (texts and rubrics, RCIA 487-504) deal with non-Catholics, whether catechized or not. In the RCIA rites, this entire section through RCIA 504 is listed as part 5. Keep in mind the various preparation rites for uncatechized baptized persons (RCIA 400-472) sometimes will precede these full communion celebrations (when we receive uncatechized Christians), sometimes not (when we receive committed and formed believers).
We’ll take these next 14 sections very slowly, with the full texts. Today, just two sections:
473. This is the liturgical rite by which a person born and baptized in a separated ecclesial Community is received, according to the Latin rite, (Sacrosanctum Concilium 69, Unitatis Redintegratio 3, Ecumenical Directory I, no 19) into the full communion of the Catholic Church. The rite is so arranged that no greater burden then necessary (see Acts 15:28) is required for the establishment of communion and unity. (Unitatis Redintegratio 18).
474. In the case of Eastern Christians who enter the fullness of Catholic communion, no liturgical rite is required, but simply a profession of Catholic faith, even if such persons are permitted, in virtue of recourse to the Apostolic See, to transfer to the Latin rite. (Orientalium Ecclesiarum 25 and 4)
How to sum up the overall approach? People who want to become Catholics may be unbaptized or baptized. The former will enter a catechumenate, unless life circumstances make this unduly difficult. As for the baptized, they may be in one or two of several categories. Baptized but uncatechized Catholics (who have not received Confirmation and First Eucharist) may benefit spiritually from the rites of part 4 (RCIA 400-472) but these are not strictly required.
Eastern Christians require no full communion rite (473-504) but they may be publicly accepted as Roman Catholics through these rituals. Eastern Christians “transferring” to a non-Latin Church in communion with Rome would follow whatever guidelines and disciplines offered there–this case is not covered in RCIA.
All other Christians (Protestants, Anglicans, evangelicals, etc.) with valid baptism will be either uncatechized or catechized. For the former group, the preparation rites of 400-472 are still optional. RCIA gives no rites, suggested or otherwise, for committed and catechized Christians wishing to become Catholic. For both groups, the principle of “no greater burden than necessary” applies. Always.
Is that clear? It may be at variance with practice in many parishes today, but it is the Church’s prescription for bringing people into full communion.