Deductions & credits

I appreciate this info.  Very informative, but I have some additional questions.  I am currently downsizing and have 30+ years of stuff to sell.  Last year I sold about 100 items, some made a profit but the remainder were at a loss.  I have a very detailed spreadsheet.  The 1099k reports the gross amount and includes sale amount, buyers shipping cost and eBay fees.  The latter two are not income to me.  In TurboTax I entered selling personal items and some were sold at a loss. I entered info on 1099k and continued.  It did not request any other info, but when I ran the check it reported an error but did not lead me anywhere.  Maybe still an issue with the software.  There should be a place where I can enter shipping cost, fees and other expenses.  Sorry for the lengthy message, but any help is appreciated.