GM said the refund would lift adjusted EBIT guidance to $13.5 billion to $15.5 billion after first-quarter profit and revenue topped Wall Street estimates.
General Motors expects a $500 million refund on Monday after the Supreme Court ruled that tariffs imposed by President Donald Trump under the International Emergency Economic Powers Act were illegal.
The Supreme Court ruled in February that IEEPA did not authorize unilateral tariffs, invalidating the "Liberation Day" levies that affected over 330,000 importers paying roughly $166 billion total.
CEO Mary Barra announced the refund expectation on Monday, while the Customs and Border Protection agency opened a refund portal last week allowing companies to claim funds within 60 to 90 days.
President Donald Trump told CNBC earlier this month he would "remember" companies that do not seek refunds, yet GM is proceeding with its application despite the political pressure.
Many other tariffs remain in effect including Section 232 duties under the Trade Expansion Act, and the administration indicated more new duties are on the way.