In the 1948 case Ford Motor Co. v. United States, the Supreme Court ruled against Ford Motor Company regarding a tax dispute. The company had been deducting its wartime excess profits taxes from its regular income taxes for several years and claimed that this was permissible under existing laws at the time of filing their returns. However, Congress later amended these laws to disallow such deductions retroactively, which led to a reassessment of Ford's tax liability by the Internal Revenue Service (IRS). The IRS argued that since Congress intended for companies not to use excess profits credits in calculating their normal tax liabilities when it passed amendments in 1943 and 1945, those changes should be applied retrospectively on all pending cases as well - including those filed before enactment of said amendments like Ford's case. Ford challenged this interpretation in court but lost both at district level and upon appeal with Sixth Circuit Court of Appeals affirming lower court’s decision. When appealed further up to Supreme Court, they upheld previous rulings stating that retrospective application did not violate Fifth Amendment due process clause nor amounted to an unconstitutional taking without compensation because there were no vested rights involved here; rather it was merely correcting what lawmakers deemed as unintended benefits given earlier through ambiguous language used initially.

The dissenting opinion in the case of Ford Motor Co. v. United States argued that the majority's decision was inconsistent with previous rulings and interpretations of tax laws, particularly those related to wartime excess profits taxes. The dissenters believed that the court had misinterpreted Congress' intent when it enacted these laws during World War II, arguing that they were meant to prevent businesses from profiting excessively from war-related activities rather than penalizing them for normal business growth and success. They also took issue with how the court calculated Ford's excess profits, suggesting a different method which would have resulted in a lower tax liability for the company. Furthermore, they disagreed with treating loans as capital contributions because this could potentially lead to double taxation on borrowed funds – once when repaid by borrower and again when distributed as dividends by lender corporation.