Yes, when using TurboTax Desktop, zoom to a worksheet for each Mercari, PayPal and eBay Forms 1099-K. No, do not add them all together.
This will be done on line 1d of Schedule C.
It may be easier to do this in Step-by-Step under the Business Tab. Follow these steps:
- Click Update by Business Income
- General Income click Start/Update
- Enter each Form 1099-K separately
For more information, see: What is Form 1099-K?