For affecting SE tax or not, I found this:

The repayment is deducted, in general, on the same form or schedule on which it was previously included. If it had been included as self-employment income on Schedule C, Profit or Loss from Business, it is deducted on Schedule C. If it had been included as capital gain on Schedule D, Capital Gains and Losses, it is deducted on Schedule D. If it was reported as wages, taxable unemployment compensation, or other non-business ordinary income, it is deducted on Schedule A, Itemized Deductions.

Here: https://www.irs.gov/irm/part21/irm_21-006-006r