To properly track and report your auction fees, you need to keep accurate and detailed records of your transactions. You should keep receipts, invoices, contracts, statements, and other documents that show the amount and date of the fees, the description and value of the items, and the name and address of the auction platform. You should also keep track of your income and expenses related to your auction activity, such as bank deposits, credit card charges, travel costs, and supplies. You should report your auction fees on the appropriate tax forms and schedules, depending on your situation. For example, if you are a hobbyist who sells personal property, you may report your fees on Schedule A as miscellaneous itemized deductions. If you are a business owner who sells investment property, you may report your fees on Schedule C as business expenses and on Schedule D as capital gains or losses.