No one in this forum has access to any of your information or to your tax returns, so no one can tell you what the problem was. If you owed tax due for a past year and did not pay the IRS, then the IRS seized your refund to pay the debt you owed. They can seize the entire refund including any child-related refundable credit you thought you were getting. The IRS sent you a letter. What tax year was that letter about? What did you do when you received that letter? Did you pay the IRS? Did you look over the tax return for that year and discover that there was an amount due? Or that you had made a mistake that resulted in owing the IRS? Do you have a cancelled check or credit card statement that shows that you paid?
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**