Another way to find it:

In any input field, hit CTRL-F. Search for the word overpayment.

The top one in the list is Overpayment credited to next year's fee.  select that field.  Hit F1 for instructions. The box that pops up says screen 37, code 18.  Is that the field you want?

(The term "code" is an anachronism, probably a vestige of the early days of programming Lacerte. Field is a better term and better understood by me.  Perhaps the kids have an even better way of describing input fields!)