Mrs Joseph said girls were already coming in to try on dresses even though ball season was three months away.
"We say to them to get in early and when they find the dress they love, to buy it, so they don't miss out."
Karen van Gysen from specialty store Bridal and Ball also had a register and extended it to red-carpet events such as the Halberg Awards.
"We have a lot of one-off designs from Istanbul and New York but there are others that we have more than one," van Gysen said.
"You can never promise that no one else will buy that dress elsewhere, but we do our best to make sure each girl has a unique look."
Ballgoers have also set up Facebook pages where photos of dresses can be posted so there are no double-ups.
Last year seniors at Whangaparaoa College set up an online ball-dress register so there was no risk of turning up in the same dress.
Former pupil Amy Johnston said the page was effective as many girls bought dresses at popular online sites so there was an increased chance of turning up in the same dress.
"All the girls that were attending the ball were invited to join the page so we could all post pictures of the dress we were wearing so people wouldn't get the same," Johnston said.
But some stores have chosen not to have a register, saying they cause more problems than they solve.
Charone Mackessack from Glamour Boutique in Newmarket said they had a register but then fielded calls from "cross mums" who were annoyed their daughter was prevented from buying a certain dress.
"We found it was impossible to ensure another girl wouldn't buy the same dress elsewhere or online anyway," Mackessack said.
"The same dress looks completely different on each girl so as long as it is not their best friend wearing it, it is not a big deal."