Make sure you file first, and make sure you Efile. Do it as soon as you can, as in the first day the IRS accepts efiling, which will probably be sometime in the first week of January. Get all your paperwork together now, so you are ready.
Once you do that, the IRS will take the position that you are entitled to the exemption, and he will have to prove you are not.
This implies that you never signed away your right to claim the child, by signing a form 8332, waiver of dependency exemption.
If you try to efile and your return is rejected, it will probably mean he claimed the child first. In that case mail the IRS a paper copy of your return, and include documentation showing that the child lived with you for more than 6 months of the year (183 days at least). It will take a while, but the IRS will sort it out and you will end up with the exemption.
Snipes
