In most cases when a person decides to have their marriage preformed in the Catholic Church it is not allowed unless both parties have been baptised. In a case where one or both parties was baptised years prior and the certificate has been lost or damaged, it is possible to obtain another copy. Other instances where it is needed to find a baptism record in the Catholic Church would include filling out a family genealogy, and learning of a person's family history.
Contact the record keeper at the parish where the baptism took place. They will look up the record and possibly provide a copy. You will need to provide the name of the person at birth, the birth date, the date of baptism if known, and the mother and father's name including the maiden name of the mother. A small fee may be included for this service. In a case where the parish is no longer in service or it is unknown, continue to the next step.
Contact the records hall through the local Archdiocese. They will direct you to the parish that took over the geographical area of the previous parish. If you are unsure of the exact location of the church a few things may help in the search. A general area where you lived during the time that the baptism took place, the priest or deacon's name that performed the service, a partial name or any other church identifiers will assist in the specific church. A list of parishes may be provided to check.
Contact each parish on the list. They will inform you if they have the record you are looking for. If they do not, continue working your way through the list until all parishes have been checked.