Hello. I sold $400 total items on Mercari for the entire year and I am wondering if I have to file that since it’s below the $600 threshold for the year? Thanks

If you sold personal items for less than you paid for them you owe no tax on that income. If you don’t receive a 1099-NEC from Mercari you don’t have to report it. 

Okay. Sounds great! Thanks! If I continue to sell in 2025, the threshold will start over since it is a brand new year, correct? Just want to make sure I am doing everything correctly!

Correct.