I'm still legally married to my husband but been separated from him for 3 years. He wants to file his taxes this year with me jointly. Can we do that even though I didn't have any earned income for this year? Also I recently had a child with another man, this man isn't involved with my child. If my husband and I file jointly can we also include this child in the taxes?

Can you file jointly? Yes, as long as you are not legally separated under a decree of divorce or separate maintenance decree. And yes - since you are the custodial parent of the child you may claim a deduction for him/her.

Note that it is LIKELY that claiming the child may make the joint return eligible for the Earned Income Credit, plus the $1,000 Child Tax Credit.

In other words, the refund from the joint return could be substantially higher (maybe as much as $4,000) than what it would have been if your husband had filed by himself.

You should be sure to get the full benefit of these credits when you determine who gets what from the joint refund.