Very few rules exist regarding what is required to claim someone as a dependent on your income taxes. However, these rules are strictly enforced. Your dependents must fit into the guidelines, or you cannot claim them as a deduction against your taxable income.
The first rule is that the dependent cannot be claimed on someone else's tax return. This means that divorced parents cannot claim the same child on each parent's return. Normally, this little rub is ironed out during the divorce process with each parent getting to claim the child on certain years. It is not uncommon for this to be put on an every other year basis.
At times, divorced parents will agree to let the other parent claim the child if a special need exists. For example, sometimes the non-custodial parent will allow the custodial parent to have one of his or her years if a large medical bill has been created by the child. The custodial parent will get to claim the child in exchange for the other parent not contributing to the medical expense. It usually is not an even exchange, but it can be better than nothing if the other parent has no resources to help with the payment.
The next rule is that the dependent must have a social security number. This number has to be listed on the form when it is filed. By putting the social security number on the return, the IRS can screen for multiple claims for the same dependent. Until about 15 or 20 years ago, this was not the case, but the IRS tightened the rules.
In order to be able to claim someone as a dependent, you must have provided one half their living expenses during the previous year. The person can be an adult or child as long as you paid for their upkeep. They cannot file their own taxes and claim themselves as a dependent. It is alright if they file, but they have to do so without claiming themselves for a deduction. They will still be able to take the standard deduction for a single or married person depending on the situation. It is just the individual deduction that is lost.
You must have some type of documentation to verify that you were entitled to the deduction if you are audited. This can simply be the child if you are the parent, your spouse is the other parent, and the child lived with you. Otherwise, you need to keep receipts to prove that you spent money on the person's upkeep. It would not hurt to have a signed paper that states that someone verified that this was true.
