Watsons acted for the seller on the deal and KWM acted for National Australia Investment Capital Limited.
Henry Davis York partner Robert Tracy said ACI's US corporate team negotiated the deal with the majority owners, Australian based investors Starfish Ventures and National Australia Capital Investment Limited.
A purchase price of US$48.75 million in cash was paid to shareholders under a complex sale structure and escrow arrangement.
ACI powers electronic payments for over 1650 financial institutions, retailers and processors, and enables US$12 trillion in payments each day, the firm said.
The completion of the Distra acquisition marks the sixth major transaction this year in the payment systems technology space for Henry Davis York.
"The payment systems market is undergoing significant change, particularly with the rise of mobile and social channels and the many new and emerging players entering into the space. Given the pace of the change, and the opportunities afforded by these channels, strategic acquisitions and partnerships are likely to continue in the short to medium term," Tracy said.