With $215.7 billion in cash reserves, Apple Inc. has a lot of money to fund its operations -- at least it looks that way on the surface. But look closer and only $15.7 billion of that cash is in the U.S. The rest is abroad and can't be used without taking a hefty tax hit.

That's why Apple is turning to the debt markets to fund everything from stock buybacks to major acquisitions, according to Tuesday filings with the Securities and Exchange Commission.

The value of the debt sale has yet to be announced. But individual debt notes are structured to pay out between 2018 and 2046. “We also plan to be very active in the U.S. and international debt markets in 2016, in order to fund our capital return activities,” Apple CFO Luca Maestri said during the company’s January investor call. He added in the same call that at the end of Apple’s holiday quarter, it had completed over $153 billion of its $200 billion capital returns program, which also included $110 billion in share repurchases.

While dividend payouts are high on the list for the use of the funds raised, Apple also proposes using its 2023 debt notes specifically for environmental purposes, such as renewable energy projects, developing “greener materials” and resource conservation.

In theory, Apple could bring back the $200 billion in cash it has overseas. But in practice, it doesn't do so because the money would be subjected to about 40 percent in federal and state taxes if repatriated, Apple CEO Tim Cook said in a December 2015 interview with CBS' "60 Minutes."

Apple debt 2018-2046 Apple's 2023 debt notes may also be used to help fund the company's environmental projects and renewable energy initiatives. Photo: Eric Thayer/Getty Images