Paymark, the largest Eftpos payments network in New Zealand, may be on the block.The shareholders of Paymark Limited told interest.co.nz they had "commenced a strategic review of their shareholdings after receiving interest in the shares. "This review is expected to take a number of months. There is no decision to sell the shares at this stage."Australia's four major banks own Paymark through their local subsidiaries. They appointed investment bankers Cameron Partners to oversee the review.The network processes around one billion transactions (worth more than NZ$48 billion) on behalf of more than 50 card issuers and acquirers every year, Paymark said at its website. It caters to more than 75,000 merchants operating 110,000 point of sale terminals.US payments giant VeriFone acquired Eftpos New Zealand (a separate network) from ANZ in 2012.