If I was baptized in another denomination, do I have to be baptized again to join this church?
The short and easy answer to this one is. . . nope!
Baptism is a once for always thing. Doesn’t matter if you were baptized as a baby or as a senior citizen. As long as you were baptized in the name of the Father, the Son, and the Holy Spirit, you are baptized. In the reformed tradition, baptism is a sacrament. The short definition of that is that it is a sign and a seal of the grace that is given to us by God. It’s a powerful moment of God moving in our lives, and it’s God doing the work, not us. There’s no need to be re-baptized because what God does stays done. And because it’s God’s work and not human work, baptism doesn’t go void or expire or anything if you move to another denomination.
Sometimes, we will have services that are a remembrance of our baptism. These serve as a public reminder that we are a people set aside by God, but they don’t make us any more baptized than we were before.
So. . . once baptized, always baptized.