While details of the tax legislation reform are yet to be finalised, Senate and House have converged over the last few days over their treatment of the estimated $1.3 trillion of cash American companies hold offshore. The vast scale of the tax cut has been the focus of discussions, based on calculations by the Financial Times and tax experts.

Read: Tax Reform: Facebook, Apple, Netflix, Google Stock Drops

Like many American companies, Apple chooses to keep the majority of its overseas earnings outside of the U.S., rather than paying the 35% corporate tax rate that currently applies if the money is brought home. According to the FT, the potential unexpected gain for the world’s most valuable company is the result of the reduced tax rate that would be applied to foreign earnings under the Republicans’ proposed reform.

The Republican proposals for reform calls for taxing past accumulated earnings at rates of no more than 14.5%, regardless of whether or not the money is returned home. Apple calculates it would be liable for $78.6 billion in taxes if its earnings were brought back under the current regime, according to the FT.

Richard Harvey, a tax professor at Villanova University who has testified before the Senate on Apple’s tax affairs, says the Senate version of the tax bill would require Apple to pay $31.4 billion on its past earnings – a full $47 billion below what it would pay today if it repatriated. That’s a number that far exceeds the annual profits of any other U.S. company.

Read: Apple Will Reportedly Be Hit With a Record-Breaking Tax Penalty

Apple’s foreign cash and investments come to $252 billion, according to ratings agency Moody’s, which is roughly one-fifth of the total overseas holdings for all U.S. companies. Microsoft (MSFT) holds the second-biggest foreign money pile at $132 billion, just over half of Apple’s.