tax hike vs tax-increase

tax hike and tax-increase both are nouns.

Word	Noun	Adjective	Verb	Adverb
tax hike	Yes	No	No	No
tax-increase	Yes	No	No	No

As nouns, tax hike and tax-increase are synonyms defined as:

Other synonyms of tax hike include tax boost.

tax hike (noun)	tax-increase (noun)
the amount by which taxes are increased	the amount by which taxes are increased