Your Spotify sales may appear as an amount less than zero if Spotify has reported artificial streaming activity on any music you have uploaded.
Spotify imposes fines for each track where over 90% of the streams were identified as artificial. As a consequence, your account balance will have been adjusted to cover these fines.
We take this matter very seriously. Engaging in illegal streaming practices violates the terms and conditions you agreed to upon registering for our service.
You must cease any artificial streaming and illegal revenue-generation activities immediately. This includes working with any music promotion companies that facilitate these activities.
Further violations will result in the termination of your account.
Check out Spotify's Artificial Streaming policy here.