No matter how studious you are with your income taxes, there's nothing you can do to control other people. Be it by mistake or a willful act of fraud, there is a chance that another taxpayer will file their return with your child. And although you may be inconvenienced by the mishap, you are not prevented from filing for your child if she has already been claimed by someone else.
How to Identify
If you someone else has claimed your child as a dependent, then you will receive error reject code 0507, indicating that your dependent has already been claimed by another taxpayer. This means that another taxpayer used your dependent’s Social Security number on his income tax return.
In many circumstances, taxpayers juxtapose Social Security numbers while e-filing. Other times, the causes could be more nefarious. The advent of e-filing has increased the possibility of fraud since there are two avenues where fraud can be committed instead of one. Either way, your main goal once discovering that your dependent's Social Security number has been used is to rectify the situation.
Divorced & Separated Spouses
Taxpayers who are divorced should usually rely on their divorce decree for instruction on who is eligible to claim the children on their income tax return. Sometimes, the judge will alternate years for filing and other times one parent will be granted sole permission for claiming the child on their return. If your ex spouse claimed your child but is not entitled to do so, attach a copy of the divorce decree to your income tax return. If your filing arrangement is not decided in your divorce decree, then you must use the Internal Revenue Service guidelines to determine which parent qualifies to claim the child. To qualify to claim the child, he must half lived with you for more than half the year, be under age 19 -- 24 if he is a full time student -- must have received at least half their support from you, and the child must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, or a descendent of one of these persons.
Once your dependent has been claimed by someone else, you can no longer e-file claiming the dependent since the e-file software cross references the system for duplicates. Print out your e-file return and mail it to the IRS office that services your area. If you are not sure which IRS office services your area, consult the IRS homepage for a complete list.