Technically speaking, there is no specific age or time period that determines when a person must stop claiming a child as a dependent. In fact, even the elderly can be claimed as dependents as “qualifying relatives” regardless of their age. However, the determination of who can be claimed as a dependent is fairly complex. There are a number of basic terms and conditions as well as a series of tests that each potential dependent has to pass before they can legitimately be claimed as dependents, although age is not – in of itself – a major determining factor.

First there are a series of conditions that must be met before anyone can be claimed as a dependent, either as a “qualifying child” or a “qualifying relative”. These are: (a) no taxpayer can claim a dependent if he or she (or their spouse if filing jointly) can be claimed as a dependent of another taxpayer; (b) a taxpayer cannot usually claim a married person who files jointly as a dependent, though there are a couple of exceptions to this rule; (c) a dependent has to be either a U.S. citizen, resident alien, national or a resident of Canada or Mexico; (d) any dependent has to qualify as the taxpayer’s “qualifying child” or “qualifying relative”. Assuming each of these initial conditions are met, then the potential dependent has to pass a series of additional requirements.

To meet the requirements of being a “qualifying child” the child has to: (a) be the taxpayer’s child, step child, foster child, sibling, half sibling, stepsibling or a the descendent of any of these; (b) the child has to be either nineteen years old and younger than the taxpayer, twenty-four years old if they are also a full time student, or can be any age if the child is permanently and completely disabled; (c) the child has to have lived with the taxpayer for at least half the year being filed for; (d) the child cannot have provided for more than half of their own support during the tax year; (e) the child is not filing a joint return on his or her on behalf (with exceptions); and (f) if the child can be claimed as a dependent by another taxpayer, the person claiming has to be the one allowed to do so.

The requirements for a “qualifying relative” are a bit different. These include: (a) the person cannot be the “qualifying child” to either the taxpayer or anyone else; (b) either the person has to be related to the taxpayer as defined by the IRS or the person has to live as a regular full-time member of the taxpayer’s household in a legal living arrangement; (c) the person’s gross annual income cannot exceed $3,650, though there are exceptions for people receiving disability payments; and (d) the taxpayer has to cover at least half of the person’s annual living expenses throughout the tax year in question, though again there are some exceptions depending on circumstances.

The exact rules and guidelines are more complex and explained in detail in IRS Publication 501. As long as your child meets all of the appropriate conditions outlined above, the child can be claimed as a dependent. Noting that many of these terms and conditions may change over the course of a year, the dependent should be retested each tax year in order to guarantee that they still qualify as either a “qualifying child” or “qualifying relative”.

The basic “long form” Form 1040 is the standard form used by American taxpayers to file their annual return. Although there are shorter, simpler forms such as the 1040A or the 1040EZ, people have to qualify to be able to file those whereas the basic Form 1040 can be used by anyone that has to file and annual tax return regardless of their other circumstances. Further, the basic Form 1040 includes the widest range of options for income tax filers, allowing the filer more ways of adjusting the numbers to their potential benefit. In fact, there are a number of tax credits and deductions that can only be claimed through the basic Form 1040.

The question of who has to file Form 1040, or one of its simpler variants, can be fairly complicated. For most people, this is determined by three factors: (a) your filing status; (b) your age; and (c) the amount of taxable income you made over the tax year in question. Both the IRS website (www.irs.gov) and the instruction book for the 1040 include a detailed chart that lay allow the relevant amounts. For example, if you are filing as single and are under sixty-five years old, you have to file a tax return if you made $9,350 or more over the tax year in question. Or, if you are married and filing jointly and both you and your spouse are over sixty-five, then you have to file a return if your income over the year amounted to $20,900 or more.

Beyond these basic qualifications, there are also a whole series of reasons that you may be required by law to file a tax return, even if you do not have to file based solely on your filing status, age, and income level. The IRS lists four primary reasons why you may have to file and annual return even if you would not have to otherwise: (a) if you owe any special taxes, like the Alternative Minimum Tax or write-in taxes; (b) if you received any Earned Income Credit (EIC) payments in advance from your employer as shown on your W-2; (c) you had earnings of at $400 from self-employment; or (d) you received at least $108.28 in compensation from a church or registered religious organization that is exempt from Social Security and Medicare taxes.

If, after all of the above, you still do not have to file an annual tax return, it may be in your best interest to do so anyway. This relates to tax credits, which will be pad to you regardless of whether you paid anything into the system. Available credits differ by year and this is particularly true at present due to all the tax credits that were included in the various economic stimulus and recovery acts that have passed in 2008 and 2009. The 2009 Form 1040 instructions list eight tax credits that you may qualify for, regardless of how much you have paid in taxes. Assuming you do qualify for any of these tax credits, you will have to file an annual 1040 in order to receive your payment, regardless of whether or not you are required to do so by law.