Get your taxes done using TurboTax

The screenshot that awesome Tax Expert @DianeW777 posted was for hobby income.

If you had $26k reported through Mercari, that doesn't sound to me like a "hobby".

Cost of goods sold is in the inventory section of Self-employment and expenses in TurboTax Self-Employed online.

• Select Federal in the left column
• Select Self-employment and expenses
• Click Review net to your business
• Click on Add expenses for this work.
• Scroll down to Less common
• Click on show more at the bottom of the screen
• Do it again
• Eventually you will see Inventory. Click Add and Continue, the Start.
• Continue until you see Let's get the costs of your goods and enter your cost of goods sold