How do I report a taxable stipend payment (I am no longer a student)?

Follow these steps to include the stipend as taxable income in your 2021 tax return.

To enter your stipend, sign in to your TurboTax account if it is not open and follow these steps:

1. Select Income & Expenses.
2. Scroll down to Less common income and select show more.
3. Scroll to the line Miscellaneous Income, 1099-A, 1099-C, and check start.
4. On the page Let's Work on Any Miscellaneous Income scroll to the line Other reportable income and click start.
5. On the page Any Other Taxable Income select yes.
6. On the page, Other Taxable Income enter the description and amount.
7. Select continue.
8. Select done on the next page

If you are not a student, what makes this income a "stipend"?  That is, who paid you and what did you do to get paid? 

@PattiF 's answer is probably correct.  But it will be entered as unearned income on line 8z of Schedule 1. Depending on you circumstances (particularly if you someone's dependent), that can cause more tax.  Depending on how earned, some stipends can be classified as earned income and should be entered differently:

Federal Taxes Tab

-Wages and income

Scroll down to:

--less common income

---Misc Income, 1099-A, 1099-C..... (Press start)

-----Select START (or update) to the 1st choice  titled "Other Income not reported on a W-2....." and Continue

-------Select YES to other wages received  and Continue

----------Select CONTINUE on the "Wages earned as a Household Employee" screen (enter nothing here)

--------------Select CONTINUE on the "Sick or Disability Pay" screen (enter nothing here)

-----------------Select "Yes" on the "Any Other Earned Income" screen and continue

----------------------Select "Other" on the "Enter Source of Other Earned Income" and Continue

--------------------------In Description Box type "Stipend" and the amount. Click Done.

That puts the income on line 1 of form 1040, where it is treated as earned income. 

Note: income on line 1 of form 1040 without a W-2 or line 1 code is a small red flag at the IRS