Apple Inc. is expected to report Tuesday that its stockpile of cash has topped a quarter of a trillion dollars, an unrivaled corporate hoard that is greater than the market value of both Wal-Mart Stores Inc. WMT, -0.80% and Procter & Gamble Co. PG, -0.67% and exceeds the combined foreign-currency reserves held by the U.K. and Canada combined.

The money, more than 90% which is stockpiled outside of the U.S., ​has drawn fresh attention as President Donald Trump has proposed slashing business taxes and a one-time tax holiday on corporate cash brought home. That could ratchet up pressure on the tech giant to make splashy acquisitions or dole out more money to shareholders.