In the United States, any individual that has received any taxable income will have to file a tax return. This means that individuals that have paying jobs through a company, self-employed individuals, and many others that receive income. If the person is unsure if they need to file a tax return should consult with a tax professional to verify.
A tax return can be filed by the person that earned the money or with a tax professional. A tax professional will be able to help the individual with receiving any deductions that will help them from having to pay in taxes.
When a person works for a company, the company will be required to take taxes out of their checks unless the individual files exempt. This is a rare case. The amount of taxes that will be taken out will depend on the amount of dependents the individual is claiming. A single person with no children are going to pay more taxes than an individual that is married with three children.
Based upon the amount of income was made, the amount of taxes due, and any deductions or credits received, is going to determine if the individual has to pay additional taxes to the IRS or receive a refund. Some individuals that did not make a certain amount of money will receive a refund on what is due to them from the IRS. This is all going to be determined at the time they file a tax return with the IRS.