My girlfriend and I had a child this year. My girlfriend is claiming our daughter, but we live together, is there any kind of tax break for me?

[Critter · Accepted solution]

Only one of you can claim the child and all the child related items if you live together. 

If you are unmarried but live together with the child, either one of you can claim the child (or children) as dependents. If the parent who claims the child as a dependent also pays more than half the expenses of keeping up their home, they can file as head of household instead of single, which is slightly more favorable.  The other parent should not even list them in Turbotax, because there are some poorly worded questions that confuse some people.

[Hal_Al]

If you and the other parent live together, either one of you (but not both) may claim the child. You may decide between you which one will claim the child. Only if you can’t agree, do the IRS tie breaker rules apply, to see who has first choice. It may be worthwhile to prepare trial returns, both ways,  to see which way the family comes out best. This tool may be useful: https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1.