home base vs main office

home base and main office both are nouns.

Word	Noun	Adjective	Verb	Adverb
home base	Yes	No	No	No
main office	Yes	No	No	No

As nouns, home base and main office are synonyms defined as:

home base and main office: (usually plural) the office that serves as the administrative center of an enterprise

Other synonyms of home base include central office, headquarters, home office.

home base (noun)	main office (noun)
(usually plural) the office that serves as the administrative center of an enterprise	(usually plural) the office that serves as the administrative center of an enterprise
(baseball) base consisting of a rubber slab where the batter stands; it must be touched by a base runner in order to score