Visa revealed in a recent SEC filing that it has secured a stake in Square's Class A stock, according to several media reports.

The card network told PaymentsSource that the stake represents 9.99 percent of "beneficial ownership" of Square's Class A common stock. Visa added that its current holdings in the mobile point-of-sale provider account for some 1 percent of Square's fully diluted common equity as of Dec. 31.

Visa announced its initial investment in Square in 2011.