There are twenty-eight auxiliary forms in English. (F. R. Palmer: The English Verb)
BE: is, are, am, was, were, ("nonfinite forms" be, being, been),
HAVE: has, have, had, ("nonfinite forms" have, having),
DO: do, does, did,
MODALS:
will, would, shall, should, can, could, may, might, must,...