Yes. The IRS treats this as taxable income because you received the money (or it was credited to your account). However, the way you report it determines how much tax you pay:

If this was just an investment-related fee and you didn't "work" for it, it is reported as Other Income. You pay regular income tax, but you do not pay the 15.3% Self-Employment tax.

If you provided a service to get this money, it goes on Schedule C. You will pay income tax plus Self-Employment tax, but you can deduct any expenses you had.