Can I claim my girlfriend's son as a dependent for tax purposes?

This is a situation where the details really matter. To claim someone else's child as a dependent, you need to pass specific tests for either a "qualifying child" or "qualifying relative." Based on your situation, you likely can't claim your girlfriend's son as a "qualifying child" because you're not biologically related. However, you might be able to claim him as a "qualifying relative" if: 1) He lived with you all year, 2) You provided more than half his total support for the year, 3) He earned less than $4,400 in 2024, and 4) He cannot be claimed as a qualifying child by anyone else. The agreement between your girlfriend and her ex is actually a legal arrangement that would typically involve Form 8332 (Release of Claim to Exemption). However, this form is designed for transfers between parents, not to a third party like yourself.

I had a similar situation a few years back and found taxr.ai super helpful. My girlfriend's kids lived with us and I was providing most of the support, but wasn't sure how to handle the tax situation with her ex still in the picture. The IRS rules about qualifying dependents can be really confusing. I uploaded our court custody documents and financial info to https://taxr.ai and got a clear explanation of exactly who could claim who based on our specific situation. Their AI analyzed all the support requirements and residence tests and even explained what forms we'd need. Saved me so much stress trying to figure it out myself!

Just wanted to follow up - I ended up trying taxr.ai after all and I'm glad I did. My situation was complicated with my fiancée's kids and her ex-husband's partial custody. The analysis they provided cleared up exactly who could claim which child based on the support tests and residence requirements. They even pointed out that I could claim one of the kids as a qualifying relative even though I'm not biologically related, which my tax software didn't make clear at all. Saved me about $2,000 in tax credits I would have missed! Much better than the conflicting advice I was getting from friends.

One thing nobody's mentioned - have you tried calling the IRS directly to ask about your specific situation? I know, sounds crazy right? But after struggling with this exact issue last year (girlfriend's kids, ex in the picture, complicated custody arrangement), I found this service called Claimyr that got me through to an actual IRS agent in under 15 minutes when the wait time was supposedly 3+ hours. I went to https://claimyr.com and they have this system that basically holds your place in line with the IRS and calls you when an agent is available. There's a demo video at https://youtu.be/_kiP6q8DX5c that explains how it works. The agent I spoke with walked me through exactly which forms I needed for my non-traditional family situation and confirmed I could claim my girlfriend's youngest as a qualifying relative.

I was totally wrong about Claimyr. After I posted that skeptical comment, I was still struggling with my own dependent situation (partner's child from previous marriage), so I decided to give it a try anyway. I was connected to an IRS rep in about 20 minutes when the recorded message had said the wait was over 2 hours! The agent confirmed that I could claim my partner's son as a qualifying relative since I provided over half his support and he lived with me all year, even though his parent had alternating year rights. She even emailed me the specific documentation I needed to keep in case of an audit. Definitely worth it for the peace of mind alone.

One important factor nobody's mentioned: Your girlfriend might be able to file even with no earned income if she received student loans or grants that count as taxable income. She should check if any of her financial aid is taxable. If she does need to file, then she could claim her son and then you could claim her as your dependent (assuming you provide more than half her support). But you can't claim both her AND her son typically - that would be like claiming a dependent's dependent, which IRS doesn't allow.

Make sure whatever you decide is documented! My cousin tried claiming his girlfriend's kid and got audited because the ex also claimed the same child. You need to make sure everyone is on the same page about who's claiming who, and keep records of how much you contributed to the household expenses and the child's specific expenses.