The "Sorry" singer and his 21-year-old fiancee have been inseparable recently, with her uncle Alec Baldwin recently claiming that the couple are already married.
However, according to editors at TMZ, the ceremony has been delayed while their teams look through the details of a prenuptial agreement that will protect 24-year-old Justin's estimated $250 million (£190 million) fortune.
Sources close to the celebrity duo have told reporters at the gossip website that they will both retain control of their own property unless they decide to put their cash together in a joint fund.
The loved-up pair sparked rumours they had already tied the knot as they visited the Marriage Bureau at the New York City Clerk's Office last week, ends September 16, - but merely obtained a marriage licence rather than making their union official.
But actor Alec believed his niece had already married Justin, as he told Access Hollywood at the Primetime Emmy Awards: "They just went off and got married, I don't know what the deal is."
Insiders have told TMZ that the wedding will only take place when the prenuptial agreement is finalised - in contrast to reports that they had defied their advisers and married without a prenup due to their religious beliefs.
A source told U.K. newspaper The Sun: "They didn't tell anyone on their teams what was going on and his people have been frantically trying to get his business affairs and finances in order."
However, Hailey has since insisted she is yet to become a married woman, writing on Twitter: "I understand where the speculation is coming from, but I'm not married yet."
The couple has also been spotted canoodling in London, with Justin photographed serenading his fiancee outside of Buckingham Palace.