Which statement about filing tax returns is true?

The statement that not every US citizen is required to file a tax return is true because filing requirements depend on various factors, including income level, filing status, and age. The IRS establishes specific income thresholds that determine when a taxpayer must file a return. For instance, if an individual's income falls below a certain level, they may not be obligated to file, even if they are a US citizen. Additionally, there are exceptions based on age and other circumstances that can influence whether filing is necessary.

In contrast, the other statements present generalizations that do not account for these nuances. It's essential to recognize that while many US citizens must file, there are significant conditions and thresholds that exempt certain individuals from this obligation. Understanding these specific guidelines is crucial for accurate compliance with tax laws.