I have a niece, living with me, that I claimed as a dependent for the past three years. Last year, I claimed her on my tax return, but the IRS sent me a letter stating that someone else had already claimed her. I know for a fact that none of her parents claimed her. What can I do? Do I have to amend the tax return as the IRS suggested or are there other means to fix this? I am the person who should claim her. I don't know who would claim her or how they got her social security number.

Write or call to see the IRS people
And explain exactly what is happening.
They have all the details , someone
Else is fraudulently claiming what is not theirs.