On 2010 returns, the amount of the adoption credit is up to $13,170, and it is fully refundable. Starting with 2010 returns, however, if you want to claim the credit for adopting a child, you’ll need to attach certain documents to your return. Without this substantiation, the IRS will disallow the credit. Because of the requirement to attach certain documents, if you claim an adoption credit, you cannot e-file your return.
In addition to filing Form 8839, also attach:
Source: Notice 2010-66
Generally, an unmarried person who maintains a household for dependents and is allowed to compute his or her tax based on head of household rates, which are more favorable than single person rates.