on an individual basis vs separately

on an individual basis and separately both are adverbs.

Word	Noun	Adjective	Verb	Adverb
on an individual basis	No	No	No	Yes
separately	No	No	No	Yes

As adverbs, on an individual basis and separately are synonyms defined as:

Other synonyms of on an individual basis include individually, one by one, severally, singly.

on an individual basis (adverb)	separately (adverb)
apart from others	apart from others