How do I handle paying state income tax for a summer internship in a different state?

You'll need to file tax returns in both states, but you shouldn't be double-taxed on the same income. Here's how it typically works: For California, you'll file a nonresident return (Form 540NR) reporting only the income you earned while working in California. Since the company already withheld California taxes, this will determine if you paid the right amount or need a refund. For Arizona, you'll file as a resident and report ALL your income, including what you earned in California. However, Arizona should give you a credit for taxes paid to California to avoid double taxation. Look for Arizona's credit for taxes paid to other states on Form 140. Make sure you keep track of exactly how many days you worked in each state, as this can affect your tax liability. Also, some states have reciprocity agreements, but Arizona and California don't have one, which is why you need to file in both places.

After struggling with a similar situation last year (internship in Washington while being a Colorado resident), I found this amazing tool called taxr.ai (https://taxr.ai) that saved me so much stress. It analyzes your specific multi-state situation and walks you through exactly what forms you need and how to fill them out correctly. I was especially impressed with how it handled my part-year residency situation. It asked questions about when I moved, how long I stayed, and then gave me state-specific advice. It even helped determine which expenses were deductible in which state, which I had no idea about before.

I just wanted to follow up after trying taxr.ai for my multi-state tax situation. I was initially skeptical (as you could see in my previous comment), but it actually solved several issues that TurboTax was giving me errors about. The tool clearly explained how my home state would give me credit for taxes paid to my work state and calculated exactly how much I was owed. It even identified a special deduction I qualified for because of my temporary work assignment that I would have completely missed! Definitely made the whole process less stressful and probably saved me from making some expensive mistakes.

If you're having trouble getting clear answers about your multi-state tax situation, I highly recommend using Claimyr (https://claimyr.com) to actually speak with an IRS agent directly. I spent weeks trying to figure out my own multi-state situation last year after working in three different states, and forum advice only got me so far. With Claimyr, they actually get you through to an IRS agent on the phone within minutes instead of waiting for hours or getting disconnected. You can watch how it works here: https://youtu.be/_kiP6q8DX5c. I was able to get specific guidance about my situation directly from the source, which was invaluable.

I need to eat my words from my previous comment. After waiting on hold with the IRS for over 2 hours yesterday and getting disconnected, I decided to try Claimyr out of desperation. Within 15 minutes, I was talking to an actual IRS agent who answered all my questions about my multi-state tax situation. The agent explained exactly how the credit for taxes paid to other states works and clarified that I needed to file my nonresident state return first. They also pointed me to specific forms and publications I needed. Would have taken me days of research to figure this out on my own. I'm honestly shocked at how well it worked and how helpful the IRS agent was once I actually got through to someone.

Something important that nobody has mentioned yet - make sure you check if California has a minimum filing requirement based on income. Some states require you to file a return even if you only earned a small amount there. With $12,800 from your internship, you're definitely over California's threshold, but this is good to know for anyone else reading who might have worked in a state for just a short time or earned less. Also, don't forget to check if your college state (Arizona) has any special provisions for students working out of state temporarily!

Has anyone dealt with California's "doing business in California" rules? I've heard horror stories about people who worked there briefly getting hit with the $800 minimum franchise tax because California claimed they were "doing business" in the state.

One thing to keep in mind is timing - make sure you file your California nonresident return (Form 540NR) before your Arizona resident return. This is important because you'll need the exact amount of California taxes you paid (from your completed CA return) to claim the proper credit on your Arizona return. Also, double-check that your employer correctly reported your California wages on your W-2. Sometimes companies mess up the state allocation, especially for temporary workers. Box 16 should show your California wages ($12,800) and Box 17 should show "CA" with the state tax withheld in Box 17. If you find any errors on your W-2, contact your employer's payroll department immediately to get a corrected W-2C. It's much easier to fix this now than to deal with amended returns later!

This thread has been incredibly helpful! I'm in a similar boat but with a twist - I'm a Florida resident (no state income tax) who did an internship in Colorado last summer. Since Florida doesn't have state income tax, I'm assuming I only need to file a Colorado nonresident return and won't need to worry about any credit calculations since there's no Florida return to file. But I'm wondering - does this make my situation simpler or are there any gotchas I should watch out for? Colorado withheld state taxes from my paychecks, so I'm hoping to get some of that back since I only worked there for three months. Has anyone dealt with the no-state-income-tax home state scenario? Also, thanks to everyone who shared their experiences and tools like taxr.ai and Claimyr - I bookmarked both of those just in case I run into issues. It's amazing how much more confident I feel about this process after reading through all these real-world examples!