I'm going through this currently, since IL has a lower threshold in effect for this year's taxes (2020 sales). I will let everyone know how painful/less it is. Definitely using an Accountant this go-round and not winging it.
Some good questions in here, such as the time between buying a selling a comic and its impact to taxes. Can I now add in packing supplies against the bottom line? Paper and ink for shipping labels, etc?
Additionally, if I did have a receipt for every comic (going back 10+ years or more), brick and mortar stores who give receipts don't usually specify at that level, it just says "Back Issue: $5". If they don't have to itemize when selling the item, and they are a full-time business, do I have to when I am buying? Perhaps it's a different tier of business versus part-time, or they are allowed to do that; I don't know, and it's all just a pain to think through. Hopefully not a pain (mentally or the wallet) to file.