I received a notice this week that Illinois never received my taxes for 2016 and now I owe $1.4k in taxes, interest, and fees. 
These taxes were paid through my job, and I know I printed out and mailed the return for that year. But now, eight years later, I’m struggling to prove that. 
I’ve been instructed to resubmit a tax return for that year, but I don’t know where to get the forms to do this. 
Everything I’m reading says the statute of limitations is 3-6 years, and I don’t know what the best course of action is. I have the W2s for that year. I can refile, but I’m going to be hit with a ton of interest and fees because I can’t prove I did file them. 
You can get the 2016 tax forms from the Illinois Department of Revenue’s website or by contacting them directly. While the statute of limitations is usually 3-6 years, some exceptions might apply, which could be why they’re still pursuing this. Since you have your W-2s, refile your 2016 return and include a letter explaining your situation. If needed, consider consulting with a tax professional to help navigate the process and potentially reduce the interest and fees.