TurboTax now handles this situation very smoothly:
-You enter the 1099-K
-On the screen "Choose which type of income your 1099-K is for", check personal item sales.
-You will get a screen to enter how much of the sales were "sold at a loss or had no gain". Most people check the box "all items were sold at a loss or had no gain".
-TurboTax makes an entry (explanation) on line 8z of Schedule 1, showing $0 (or the calculated amount if some were sold at a profit) as the taxable amount.
Don't worry if you don't have receipts. This is a common enough situation that an IRS inquiry is unlikely. Consider taking photographs of the items sold, to show that they were used household items.
