Every unbaptised person, and only such a person, can be baptised.
Regarding Baptism of adults (and those over the age of reason, i.e. normally, 7 years of age or more)
To be admitted to Baptism, an adult must have manifested the intention to receive Baptism, must be adequately instructed in the truths of the faith and in the duties of a Christian, and tested in the Christian life over the course of the catechumenate. The person must moreover be urged to have sorrow for sins.
You will also need to provide the sponsors' certificates of:
Regarding Infant Baptism (normally, those under the age of 7 years)
Parents are obliged to see that their infants are baptised within the first few weeks. As soon as possible after the birth, indeed even before it, they are to approach the parish priest to ask for the sacrament for their child, and to be themselves duly prepared for it.
For an infant to be baptised lawfully it is required:
- that the parents, or at least one of them, or the person who lawfully holds their place, give their consent;
- that there be a realistic hope that the child will be brought up in the catholic religion.
You will also need to provide:
- The Baptism certificates of the parents (or legal guardian)
- The Baptism and Confirmation certificate/s of the sponsors
Note: This can be a good opportunity for parents to receive Sacraments they may have missed or never had an opportunity to receive.
I can't find the sacramental documents! What do I do?
Contact the parish where the person was baptised. Details of the sacraments a Catholic receives ought to be recorded in the Baptism Register.
Otherwise, contact the parish where the Sacrament took place, e.g. If a person was Confirmed at a different Church, they might have a record.
Lastly, if all else fails, call on the godparents or other witnesses of the Sacrament to provide testimony of what took place. Photos can be very helpful. Contact Our Lady of the Assumption parish, if you need further assistance.