Final answer:
To determine the filing requirement for a nondependent, one must consider age, income, and marital status. These factors establish if an individual must file tax returns and which tax bracket they fall into.
Step-by-step explanation:
The three factors needed to determine the filing requirement for a nondependent are age, income, and marital status. These are crucial in determining whether an individual meets the criteria to file tax returns independently. For example, in the case of age, individuals under certain age thresholds may have different filing requirements than older taxpayers. Income is another key factor; it determines if the gross income is above the IRS filing threshold. Lastly, marital status impacts the filing status and threshold levels at which one must file a tax return, such as 'Single' or 'Married Filing Jointly'.