In some cases spanking scenes were shot, but didn't make the cut.
This seems to be the case for EXCESS BAGGAGE from 1928.
Here's the source (along with the picture below):
From William J. Mann’s 1998 biography of William Haines, Wisecracker:
Several spanking scenes between Billy and Josephine, especially one in which he deliberately lifts her skirts first, were trimmed back or excised completely.
So we will only see William Haines spanking Josephine Dunn (22) only in this picture: