Solicitec and SoS have a 12th order for Integration Partner, which links the two suppliers' Windows products, six months after its launch.
Integration Partner provides real-time integration between the SolCase case management system, devised by Solicitec, and the SoS Practice Manager accounts system.
The firms say they design ed the product to maximise efficiency and accuracy in data entry while retaining cashier control of transactions.
The latest firm to buy the system is Hancock & Lawrence of Truro, Cornwall.
Mark Woodward, sales director at Solicitec, said: "Solicitec and SoS are both keen watchers of trends in information technology and we are firmly of the opinion that the legal market is about to change radically.
"To maintain user choice and safeguard market positions, both firms believe that collaboration and co-operation between software suppliers is the only way forward."
Woodward added that Solic itec and SoS were keen to see as many other developers as possible take up the standard and jointly develop it to keep pace with the latest ideas and technology.
He said that the current integration standard was seen as the first step in the development of the software.