Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Do I need to prove 'Garage Sale' items incurred a loss
-Alain Wertheimer I'm a hobbyist... Most (probably all) of those older items were sold both prior to my establishing the LLC This is a hobby of yours, this is not your business. You purchased all of these goods for your pleasure, not for their future profit. The later items that you bought after your LLC was establish served both purposes (perks of doing what you love).  How should I go about reporting this income for the items I don't have records for how much I purchased them for?  There's nothing you can do. As noted above, these items (if you were to testify in court against the IRS). "Losses from the sale of personal-use property, such as your home or car, aren't tax deductible." Source Do I need to indicate 100% of the income because I can't prove that I sold it at a loss? Yes, if you do not have previous records you must claim a 100% capital gain. Source Addition: As JoeTaxpayer has mentioned in the comments, the second source I posted is for stocks and bonds.  So at year begin of 2016, I started selling what I didn't need on eBay and on various forums [January - September]. Because you are not in the business of doing this, you do not need to explain the cost; but you do need to report the income as Gross Income on your 1040. Yes, if you bought a TV three years ago for a $100 and sold it for $50, the IRS would recognize you earning $50.  As these are all personal items, they can not be deducted; regardless of gain or loss. Source Later in the year 2016 (October), I started an LLC (October - December) If these are items that you did not record early in the process of your LLC, then it is reported as a 100% gain as you can not prove any business expenses or costs to acquire associated with it.  Source Refer to above answer.  Refer to above answer.  Conclusion Again, this is a income tax question that is split between business and personal use items. This is not a question of other's assessment of the value of the asset. It is solely based on the instruments of the IRS and their assessment of gains and losses from businesses. As OP does not have the necessary documents to prove otherwise, a cost basis of $0 must be assumed; thus you have a 100% gain on sale.