First, I would go back to the preparer that you paid to do it correctly. If, in fact, you did qualify for HOH and they failed to ask you about it, they should do it for you (for free I would hope).
Otherwise you would need a copy of the tax return, the 2011 software and then enter the information exactly as it was filed, claiming single and generate a 1040 form exactly as it was filed. Then, you could amend that to change to HOH so the amended 1040X contains the changes.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
