tax-increase vs tax hike

tax-increase and tax hike both are nouns.

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

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

Other synonyms of tax-increase include tax boost.

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