Since a celebrant-led ceremony isn't legally binding, most couples who opt for a celebrant tend to go to their local registry office a couple of days before their wedding, to do the legal paperwork, and then they're free to have their celebrant wedding celebration wherever they want.

My name is [Celebrant's full name] and I am duly authorised by law to solemnise marriages according to law and to officiate at your marriage today. I take this opportunity to wish you both much happiness in your future lives together.

Much like wedding celebrant, wedding officiant is a broad term to describe someone who leads a wedding ceremony. Not everyone who refers to themself as a wedding officiant can legally register your marriage, however, some solemnisers who can legally register your marriage (see What Does a Wedding Solemniser Do?)