In 1991, at the age of 18, Kuprii became the founder and director of the small OSBEND enterprise. For almost 4 years, he sold office equipment, clothing, and video equipment.
At the end of 1994, Kuprii started importing goods from Turkey and was doing it for almost 10 years. In the beginning, he was selling outerwear in the Dnipro city and Kamianske markets. The following year, he about had 20 people working for him.
In 1997, Kuprii and his family purchased a shop in the centre of Kamianske to sell clothing.
In 2004, he leased the store and started to work in real estate and outdoor advertising business.
Until 2006, Kuprii worked on the election campaigns of the Our Ukraine political party in its central office in Kyiv.
In 2008, he ran for the off-year election of Mayor of Kamianske.
In 2010, Kuprii was elected a deputy of Kamianske city council on the list of the political party «For Ukraine!«. At that time, he was a member of the party.
In 2012, he ran as an unaffiliated candidate in the elections to the Verkhovna Rada of the 7th convocation in the 30th district (Bagliyskiy, Dniprovskyi, part of the Kamianske Factory District).
In 2012-2014 he was a member of Svoboda political party.
Kuprii was a member of Parliament of Ukraine of the 8th convocation in constituency No. 29 from the political party European Solidarity.
Since 2015, he is not part of any faction.
Now, he is a head of the board of Committee on Legislative Support for Law Enforcement in Verkhovna Rada. He is currently working on creating his own party.
In 2019, he ran for President of Ukraine as an unaffiliated candidate.
Associated with Kolomoisky
Kuprii is one of the active public lobbyists of Kolomoisky's interests. They met in 2014, when Kolomoisky headed Dnipropetrovsk regional state administration. At the time, Kuprii was his adviser on the fight against corruption and organized crime.
When Kuprii ran for Verkhovna Rada, a number of media directly called Kuprii a “Kolomoisky man”. In Parliament, it was Kuprii who sent deputy inquiries to the Prosecutor General's Office to find out whether there were any criminal proceedings against Kolomoisky.
Kuprii is the head of the Ukrop Party, which was a project of Korban and Kolomoisky.