In the case of Flora v. United States, 1957, the U.S Supreme Court ruled that a taxpayer must pay the full amount of an assessed tax before filing a lawsuit to recover any part of it. The plaintiff, William J. Flora had been assessed for additional income taxes and penalties by the Internal Revenue Service (IRS). He paid part but not all of this assessment and then sued in federal court for recovery on grounds that he was overcharged. However, his suit was dismissed because he hadn't paid off his entire debt first as required by law under Section 1346(a)(1) which states "no suit shall be maintained in any court for recovery until such tax has been fully paid". This decision upheld what is known as 'the full payment rule' - reinforcing that taxpayers cannot sue until they have completely settled their debts with IRS.

In the dissenting opinion for Flora v. United States, Justice Whittaker argued that a taxpayer should be allowed to sue for a refund of part of an assessed tax without having to pay the full amount first. He contended that this requirement could lead to undue hardship and potential bankruptcy for taxpayers who cannot afford to pay their entire tax bill upfront before challenging it in court. Furthermore, he believed that such a rule was not supported by either statutory law or prior case law and pointed out inconsistencies in how different courts had interpreted relevant laws on this issue. He also expressed concern about the implications of requiring full payment before allowing legal challenges, arguing it would effectively deny many individuals access to justice due its financial burden.