The New Zealand woman, 28, told police she had been sexually assaulted by at least three men after she organised to meet a man she had been chatting to through the dating app on Saturday night.

The woman, who was on a business trip, said she had met the stranger at a Kings Cross restaurant before going with him to a bar in Martin Place.

NSW Police said the woman retracted her statement on Thursday night and, after a five-day investigation, police had decided there was not enough evidence to follow through with any charges.

"As a result, the investigation into the alleged sexual assault, which was being led by the Sex Crimes Squad, has now concluded, pending any further information being provided," a NSW Police spokesman said.

Police would not comment on whether the woman had fabricated the story.

Sex Crimes detectives stressed they did not want the woman's retraction to stop anyone else who had been been sexually, indecently or physically assaulted in any way to report the matter to police.

"All reports are treated seriously and are thoroughly investigated," police said.

The woman previously told police she felt dizzy, numb and lost her bearings shortly after a few of her date's friends arrived at the Martin Place bar.

She said she was sexually assaulted by at least three men and later found herself in a property near Botany but had no idea where she was.

The woman allegedly told her work colleagues what happened and they contacted police.

After being treated at hospital on Monday, the woman gave a formal statement on Tuesday.

She has now returned to New Zealand.

Tinder is a dating app linked to people's Facebook pages and informs users of who is single in the area nearby.

One swipe right to the green heart registers your interest. One swipe left to the red cross says "nope".

If two users like each other's photos, you get "match" and conversations can begin.

"The vast majority of people who use dating websites and apps do so for the right reasons, but there are a number of sexual predators out there who use modern technology to find potential victims," Detective Inspector Michael Haddow said.

Detective Inspector Haddow suggested those meeting strangers online should think about bringing a friend along and meeting in a public place.

"If it's not possible to bring a friend with you, then, at the very least, stay in regular contact with a family member or friend, keeping them abreast of how the night is going and where you may be heading to."

NSW Rape Crisis Centre executive officer Karen Willis said most people who reported sexual assault had been the victims of a serious crime.

"The old days of people not being believed are gone," Ms Willis said.

"Police know that, overwhelmingly, when people report sexual assault they are reporting a serious crime that's occurred," she said.

Ms Willis said some victims chose to focus on their recovery and were not able to go through a long, traumatic court process.

"It does take a long time [for cases] to [make] their way through the criminal justice process and that does mean for some people they make a decision to work towards their recovery rather than press ahead with court proceedings."

While the process of reporting sexual assault was difficult, she encouraged it.

"While we understand the process is really difficult, there are lots of support systems in place for people to make a choice to report and NSW Police see this work as an absolute priority."

NSW Rape Crisis line: 1800 424 017