Amazon.com Inc., the world's largest online retailer, is planning to issue $3 billion of debt to help finance the purchase of its Seattle headquarters in its first bond offering in more than a decade.

Amazon, which has no bonds outstanding, may sell $750 million of three-year notes that yield 38 basis points more than similar-maturity Treasuries, $1 billion of five-year debt with a 63-basis-point spread and $1.25 billion of securities maturing in 10 years that yield 93 basis points more than benchmarks, according to a person familiar with the offering who asked not to be identified citing lack of authorization to speak publicly about the transaction. A basis point is 0.01 percentage point.

Proceeds will be used for general corporate purposes including the $1.16 billion real-estate transaction, according to Moody's Investors Service, which rated the bonds Baa1, three levels above speculative grade.