Wal-Mart Stores, Inc. (NYSE: WMT) will cash in nicely if the planned GreenDot Corp. IPO goes well. On June 2, 2010, GreenDot filed an amendment to their S-1/A filing with the SEC. In the amendment, GreenDot provided updated financials (through March 31, 2010) as well as details of a stock grant to WalMart.

WalMart and GreenDot have enjoyed a long relationship. GreenDot has been the exclusive provider of the general purpose reloadable prepaid debit cards sold at Walmart since Walmart initiated its Walmart MoneyCard program in 2007.

In GreenDot’s most recent quarter, operating revenues derived from sales at Walmart represented 63% of GreenDot’s total operating revenues (significantly higher than other retail distributors).

The relationship may pay off handsomely for Walmart if GreenDot’s IPO plans are successful. In the recent S-1/A, GreenDot announced that it issued to Walmart 2,208,552 shares of GreenDot’s Class A common stock. Apparently, this grant provides Walmart with less than 1% of the outstanding Class A common stock. However, the grant could add up to a big win for Walmart.

GreenDot retains a right to repurchase the shares at $0.01 per share if the commercial agreement between GreenDot, Walmart and GE Money Bank is terminated. The Walmart shares vest (or, put more accurately, the repurchase right expires) at a rate of 36,810 shares per month over the five year term of the commercial agreement.

GreenDot continues to be a leader in the general purpose reloadable prepaid card space. According to their S-1/A:

We believe that we are the leading provider of GPR cards in the United States based on the 3.4 million active cards in our portfolio as of March 31, 2010, which we define as cards that have had a purchase, reload or ATM withdrawal transaction during the previous 90-day period.

Read the full S-1/A here.