US credit card issuer Visa Inc. said Monday it is buying back its former subsidiary Visa Europe in a 21.2-billion-euro ($23.5-billion) deal identifying increased scale and efficiency.

The deal, approved unanimously by both boards, will be carried out in two stages -- an initial payment of 16.5 billion euros followed by a possible additional payment of 4.7 billion euros four years after the agreement is finalised, Visa said.

UK-incorporated Visa Europe, operated by member banks and other payment service providers from 38 countries, was founded in 2004 and fully gained independence of Visa International Service Association in October 2007 when Via Inc. went public on the New York Stock Exchange.

In a statement, Visa said the deal, subject to regulatory approvals and expected to close in Visa Inc.’s fiscal third quarter of 2016, would give global clients a "more seamless" experience.

"We are very excited about unifying Visa into a single global company with unmatched scale, technology and services,” said Charles Scharf, Visa Inc.'s chief executive, who added the deal would benefit financial institutions, cardholders, employees and shareholders alike.

"The Visa Europe team has done a tremendous job building a leading payments system that is trusted and respected across Europe, and together we will bring the power of electronic payments to more people, in more places, than ever before.”

Nicolas Huss, Visa Europe's chief executive, added integrating the two businesses would provide the "financial strength and operational scale necessary to accelerate the next generation of payments throughout Europe."

Gary Hoffman, Chairman of the Visa Europe Board, said "...a combined Visa will be better positioned to serve the needs of customers going forward.

Visa stated the transaction would afford a significant growth opportunity as mobile payments continue to grow with the increasing availability of Near Field Communication technology and new mobile payment platforms.