Coca-Cola asked a federal appeals court Thursday to overturn a U.S. Tax Court decision that put the company on the hook for more than $20 billion in taxes and interest, contending that the Internal Revenue Service engaged in an unfair and retroactive bait-and-switch in how it calculated Coke's foreign profits.

The IRS challenged Coke's tax returns for 2007 through 2009, and the outcome of the case will affect the company's payments for every year since then. Gregory Garre, arguing for the company before a three-judge panel in Miami, pointed to a 1996 Coke-IRS agreement and subsequent IRS statements that accepted the company's method for calculating how much profit was assigned to the U.S. and how much was attributed to lower-taxed foreign countries.

Judge Barbara Lagoa expressed concerns that the IRS actions were retroactive, and Judge Nancy Abudu asked why the IRS had challenged Coke's operations in some countries but not others.

Garre contended that the IRS chose countries where the U.S. lacks certain treaty arrangements, because countries with treaties could have negotiated for some of the taxes.

"There's nothing in the record to support that," said Jennifer Rubin, a Department of Justice attorney. "That's a conspiracy theory."

Rubin said tax enforcement is, by nature, retrospective. She discounted post-1996 statements that indicated acceptance for Coke's disputed profit-split method. And she argued that Coca-Cola could have attempted to negotiate a forward-looking agreement with the IRS.

A decision from the appeals court could take months and may require further consideration by the Tax Court.