Gay couples whose relationships will be legally recognised from December are piloting an online civil registration system for England and Wales.
Registrars will record civil partnerships on a new web system
It is eventually expected that all births, deaths and marriages will be recorded via Registration Online.
Brighton and Hove's register office is trialling it with some of the 400 same-sex couples on its waiting list.
The system will also be used for pilot purposes in Bath, Liverpool and Swansea over the next fortnight.
Brighton and Hove will begin the registration of civil partnerships from 0800 GMT on 21 December, after the Civil Partnership Act becomes law on 5 December.
The Reverend Debbie Gaston and her partner of 16 years, Elaine Cook, will be one of the first same-sex couples to take part.
They have been involved in "testing the robustness" of the online registration system with Brighton and Hove's superintendent registrar Linda Holm.
Another couple taking the part in the pilot were Sussex Police employee Roger Lewis and his partner Keith Willmott-Goodall.
Ms Holm said: "Obviously the first day it was very new and it threw up some things in the system that needed to be looked at.
"But basically it is something we'll just get used to. It is paving the way for a modern registration service."
Births, deaths and marriages have been registered with pen and paper since 1837 and Ms Holm said there would still be a manual back-up when the new web service is used for real.