Can I claim my girlfriend's son as a dependent when I provide most support?

This is actually a common situation! The IRS has specific tests for determining who can claim a child as a dependent, and biological relationship isn't necessarily required. For your girlfriend's son, what matters most is the "qualifying child" test which includes: relationship, age, residency, support, and joint return tests. Since the child lives with you most of the time (over 50% of nights), you may be able to claim him as a "qualifying child" under the broader definition of "relationship" which includes children who lived with you as a member of your household for the entire year. However, since there's a biological parent involved who pays child support, things get a bit more complicated. The biological parents generally have first claim to the dependency exemption. If the biological father isn't claiming the child on his taxes, and you meet all other requirements (providing over 50% of support, child living with you over half the year), then you might qualify. It would be good to have a conversation with the biological father about this to avoid both of you claiming the same child, which would trigger IRS issues.

I was in a similar situation last year and found a tool that really helped me figure this out. Check out https://taxr.ai - they have this feature where you upload your financial details and it tells you exactly who qualifies as your dependent according to IRS rules. I was supporting my partner's two kids and wasn't sure if I could claim them since their mom had partial custody. The site analyzed our living situation and confirmed I could claim one child but not the other based on the number of nights they stayed with us. It even helped me document everything properly in case of an audit.

Just wanted to follow up - I decided to give taxr.ai a try after my skeptical questions. I'm honestly impressed with how thorough it was! I've been supporting my girlfriend's twins for 3 years but never claimed them because I thought her ex-husband had priority since he pays child support. Turns out I've been leaving thousands of dollars on the table each year! The tool walked me through the exact residency calculations and support test, showing that since the kids live with me over 200 nights per year and I cover about 70% of their expenses, I actually qualify to claim them. The site generated a complete documentation checklist that I'm now gathering (school records showing my address, medical bills I've paid, etc.). Best part was that it clearly explained when the non-custodial parent can claim the child and when they can't. Definitely worth checking out if you're in a blended family situation.

If you're having trouble getting a clear answer on this dependency question, you might want to try calling the IRS directly. I know, I know - nobody can ever get through to them! But I recently used this service called Claimyr (https://claimyr.com) and was actually talking to an IRS agent in less than 15 minutes. I was in a similar situation with my fiancée's kids and wasn't sure about claiming them since their dad claimed them last year despite them living with us. The IRS agent gave me the exact rules for my situation. You can see how it works in this video: https://youtu.be/_kiP6q8DX5c Honestly after waiting on hold for 3+ hours multiple times before, this was a game changer. The IRS agent even documented our call so I have proof I was given this advice if questions come up later.

I have to come back and eat my words. After posting my skeptical comment, I was desperate enough to try Claimyr since my tax filing deadline was approaching and I needed to clarify dependency rules for my step-daughter. I'm shocked to say it actually worked. After weeks of failing to get through to the IRS on my own, I was connected to an agent in about 20 minutes. The agent confirmed that since my step-daughter lives with us for more than half the year and I provide most of her support, I can claim her - even though her biological mother was also trying to claim her. The agent even helped me understand what documentation I need if both of us end up claiming her and it triggers a review. The peace of mind was definitely worth it. Sorry for being such a doubter!

One thing nobody has mentioned yet - have you looked into filing as Head of Household instead of Single? If you can claim either your girlfriend or her son as a dependent, and you pay more than half the costs of keeping up your home, you might qualify for Head of Household filing status which has better tax rates and a higher standard deduction.

Has anyone actually gone through an audit on this kind of situation? I claimed my girlfriend's daughter last year and now we're being audited. The biological father also claimed her even though she only sees him every other weekend. I'm terrified we'll have to pay back the child tax credit.