How do i treat the sale of several guitars that were bought 10 years ago and sold in 2023?

[randwohl]

Sold guitars through 3rd part platform Reverb.com. I'm not a dealer and not a business. One was sold at a profit and several were sold at a loss.

[PaulaM]

Losses on personal property won't be recognized but the gain is. 

Enter in the Investment section and choose personal items as your category. Since you know you had losses on several, enter only the one you had a gain. You'll enter its purchase costs, proceeds, etc.