Northern Ireland will become the first part of the UK to criminalise paid-for-sex.
Those who break the law will face up to one year in prison.
The Northern Ireland Assembly has passed the Human Trafficking and Sexual Services Bill, which includes criminalising the purchase of sex.
Prostitution is currently legal in the UK and most EU countries, while many aspects of the trade, including brothels and public solicitation, are illegal.
The move in Northern Ireland echoes laws already in place in Scandinavian countries that opts to make customers guilty of crimes, rather than the prostitutes.
The Republic of Ireland is considering similar laws.
A former cabinet minister has urged parliament to consider making the purchase of sex illegal and called on male politicians to speak about prostitution.
Caroline Spelman, Conservative MP and ex-Environment Secretary, told the Guardian newspaper she was in favour of the legal model seen in Sweden, Iceland and Norway, despite warnings that it could push the trade 'underground'.
"I think the Nordic law is the right direction, but we need cross-party support for it," she said. "It's very important men come out and say what they think as well because it's very emotive."
While kerb-crawling, soliciting and the running of brothels is already illegal in England and Wales, but selling sex is allowed behind closed doors.
Buying sex is legal on the proviso that a third party has not "engaged in exploitative conduct of a kind likely to induce or encourage" the sale.