Never did that bank, per se. But I think I recall there are two types of checks that you want to identify as voids, Voids, of course, and Reversals. And how you treat them varies from bank to bank. Some want them omitted. Some don't want a negative sign, some do.
Rant: If ever there was a file type to standardize amongst all institutions, why for the lovva god don't they standardize ACH and Positive Pay!