@whiteswantrading
If you are selling personal items for less than their original cost, this is not an investment. You can’t deduct a capital loss on personal items. The instructions for how to report a 1099-K as non-taxable income using a second negative adjustment will work, but may result in an IRS letter asking more questions. The IRS instruction in this situation is to leave the 1099-K off your tax return, file by mail, and attach a copy of the 1099-K and an explanation as to why it is not taxable income.
If you have a gain from the sale of personal property, then you must determine whether you are operating a “ongoing trade or business“ or this is a hobby. If it is an ongoing trade or business, then you need to report the gross income on schedule C and your cost of items would be your cost of good sold. If it is not a schedule C business, then you would report the gains from the sale of personal items on schedule D and you cannot deduct the losses of personal items.
You would indeed be expected to add the transaction details of each item separately. If you have sold so many personal items for gain that you can’t add that many transactions, you might reconsider that you actually have a schedule C business.
