The transaction is expected to close by the end of September, after obtaining approval from banking regulators.

Union Bank’s president and chief executive officer Masashi Oka said the acquisition of Smartstreet will enhance its position as a leader in providing banking services to a niche industry where the bank has a deep knowledge and a long track record of providing excellent service.

"Providing financial services to companies that manage homeowners associations and other community associations is a core segment for Union Bank’s Global Treasury Management, and we’re already the leading provider on the West Coast," Oka added.

"HOA banking is a valuable source of long-term core deposits. This is a great example of how Union Bank’s strong and stable balance sheet allows us to pursue opportunities that will provide immediate benefits and support responsible future plans."

Smartstreet has nearly $1bn in deposits and a complete receivables offering and lockbox operations, which serves over 460 management companies and 15,000 associations in 36 states, across the US.

As per the merger agreement, Smartstreet will operate as a division of Union Bank and will retain its Smartstreet brand in the HOA markets and its executive team.

As of 31 March 2012, UnionBanCal Corporation owned assets of $92.3bn and offers a wide range of financial services to individuals, small businesses, middle-market companies, and major corporations, through its subsidiary Union Bank.