Apple Inc. (AAPL) has avoided as much as $9 billion in taxes by financing part of a $55 billion stock buyback with debt rather than offshore cash that would have been billed by the U.S. government, according to Moody’s Investment Services and Bloomberg estimates.

Based on current rates, Apple will pay interest of about $308 million a year on the $17 billion bond offering, said Gerald Granovsky, a senior vice president at Moody’s. He also added that if the funds had come from Apple’s offshore cash pile of about $100 billion, the Cupertino, California-based iPhone maker would have had to pay a 35 percent tax to repatriate the money. That means Apple avoided about $9.2 billion in taxes. And since interest payments are tax-deductible, that’s another $100 million a year.

Looks like Apple has executed excellent financial prudence.