"jointly purchased" is correct and usable in written English.
You can use it when referring to something that was bought by two or more people together. For example: "My parents and I jointly purchased a new house."
Trafigura, a Dutch trading house, and Mubadala, an arm of Abu Dhabi's government, jointly purchased another port.
Since starting with the air van, the departments have jointly purchased gear and tools and shared in the cost of hiring auto mechanics.
The National Gallery in London and the National Galleries of Scotland jointly purchased two masterpieces by Titian a few years ago.
In 1999 Lemieux converted years of his unpaid Penguins salary to equity and led a group of investors that jointly purchased the team.
The two have jointly purchased Mr. Hirst's installation, titled "School: The Archaeology of Lost Desires, Comprehending Infinity, and the Search for Knowledge," for $10 million for the Lever House Art Collection.
In November, 1906, Sinclair and his group jointly purchased a former boys' academy in Englewood, New Jersey, named Helicon Hall, after the mountain in Greek mythology whose rushing springs inspired the Muses.
We arranged for the two commuter railroads, the Long Island Rail Road and Metro-North, to save money by jointly purchasing equipment and supplies.
Poland's prime minister, Donald Tusk, has revived an idea about the EU jointly purchasing its energy from Russia to provide the bloc with more bargaining muscle.
THIS week's issue of The Economist includes an article on a scheme in which supporters of the Portsmouth football club could jointly purchase the team.
The two companies, respectively, the third and fourth largest motorcycle brands in Japan, will jointly develop motorbikes, supply each other parts and products, and jointly purchase parts and materials.
In the letter on Nov. 10, the two companies wrote that they would address the "key operating challenges facing" Sprint and significantly cut costs by jointly purchasing handsets and examining network infrastructure.
