Thanks for the reply. Based off the turbo tax help page I linked in my post, I reported it in TT as "Other income not already reported on a Form W-2 or Form 1099". Boxes 1 and 2a are the same (fully taxable), and the contributions were to a traditional 401k (coded D on W2 Box 12). In my 1040, boxes 5a and 5b are empty, as I did not have the 1099 at that time. The $37 is included in line 1 of my 1040, and specified on my "Wages, Salaries, & Tips Worksheet" under line 9b, with a custom label of "2021 Return of excess 401(k) deferral".
