The National Secular Society in the United Kingdom issues De-baptism certificates. These are used by people who renounce their baptism. Those people may also choose to have a note added to the Church registrars to the effect that they have left the Church and are not to be counted as members anymore.
Some have ridiculed this practice of De-baptism on the grounds that the fact that if you were baptised then your baptism is a fact and still happened. But the ceremony may have happened but that does not mean any genuine baptism took place. The ceremony is only outward but you can't see the power it gives. It may not even give those powers - for example, if the priest serves the devil he may not intend the blessings of baptism to be transmitted to the child. Then though the ceremony has taken place no genuine sacrament of baptism has been administered. If a genuine baptism does not take place, then no genuine initiation into the Church takes place. The result is a person who may only imagine they are real members of the Catholic community. Obviously there is no way to test if a person is really a member.
It is not really baptism, strictly speaking, that has the alleged effects. The Church believes that baptism is a sign that God is working in the person. The water and the ceremony have no power in themselves. It is just that God has decreed he will work when the ceremony is done. That is what the Church means when it says that if the priest baptises then strictly speaking it is really Jesus who baptises or God.
It is really the initiation conferred by baptism that needs to be reversed. The baptism itself is only a sign that God and the Church are possibly initiating a child. I say possibly because God does not confer valid baptism if the priest intends it to be a pretence. Rather than de-baptism the emphasis should be de-initiation.
The Church believes babies have no sin they have committed themselves but they have original sin - an inherited rejection of God. If that sin keeps them out of God's community and reversing it puts them into the community then surely a baptised person who sins greatly is not a true member of the community? They are more hostile to God than any baby could be and they know what they are doing! Then the baptismal grace is totally ruined. One would need to be baptised again to get it back but God settles for accepting the original baptism instead of requiring that. In your heart you are being rebaptised. That is what the Church means when it says you must live out your baptism every day.
The Church says that the effects of baptism include making you a child of God and a member of his Church and cleansing you of all sin including original sin. If you are an adult and you go through baptism without intending to receive any of the effects then the baptism is null and void. It only looks like a baptism. The baptism is as invalid as a baptism performed on television by an actor in the role of a priest. The baptism will have to be repeated when the person has the proper dispositions. Then the baptism will be valid.
De-baptism should be about renunciation of the meaning and effects of baptism. It should be about retrospectively making the ceremony null and void.
If you really had original sin as a baby then it follows then that left to yourself you would renounce God if you were developed enough to know what you were doing. You can't consent. But original sin inclines the child to want to do evil and do good without reference to God. Without consent we have to go by the nature of the child. If the child has original sin then that has to be treated as consent not to be baptised. Infant baptism then is a powerless ceremony. It has no binding authority.
It is very sly of priests, especially Catholic priests, to have parents bringing babies to them for baptism when those parents are not making an informed decision. There is no discussion about the problems of baptism. The parents are only given the Catholic side of the story. Catholic priests make incredible claims for baptism, stronger than that of most Protestant Churches, which is why I refer to them as especially manipulative and sly. They say baptism is the biggest step in life for the child and yet they don't act consistently with this assertion. They are like suitors who wish to rush the women they want to marry to the altar before the women can think about it properly.
If the priests were honest enough to be blunt and to say, "Your baby is a bastard and it doesn't belong to God but we can fix that in baptism. God doesn't have a relationship with it for it has original sin", many people would think twice. It might sound unkind for priests to be that honest. But if what they teach about baptism is true then it is not.
Baptism is intended to marry the baby to the Church. If that is not a null wedding then nothing is!
The Church says that a mark is put on you by baptism. If baptism has power, all the power can be rejected and renounced. When that happens, the baptised person is in the same situation as an unbaptised person except that there is a mark. What is the mark for? It is a sign that the baptismal power can be reactivated and retrieved if the person repents. The person might have been physically baptised but physical baptism is a symbol of spiritual baptism. The spiritual side is really what it is all about. If that is all renounced, then the baptismal effects have been undone. Only the mark and the fact that a physical baptismal ceremony happened remain. But you are effectively de-baptised.
Your choice with regard to religious membership when you know what you are doing takes priority over any choice made by your parents and godparents to enter you into such membership. A choice made for you cannot have the same force as one made by you. Your personal choice matters most. So if you reject the religious membership that baptism gave you, you should be annulling your baptism. God is almighty and nothing can violate his will not even the sinner for God then permits the sin to happen. So God knows if a baptised baby will accept the choice made for her or him. Seeing a rejection means that God will have to regard the consent of the godparents and the parents as invalid and not impart membership of the church on you.
De-baptism can be seen as a declaration that though a ceremony happened it was just mumbo-jumbo and you are unwilling to be listed as a member of a Church over it. However, a baptism annulment certificate would make more sense and be a better idea. It is clearer.