taxation vs tax income

taxation and tax income both are nouns.

Word	Noun	Adjective	Verb	Adverb
taxation	Yes	No	No	No
tax income	Yes	No	No	No

As nouns, taxation and tax income are synonyms defined as:

Other synonyms of taxation include revenue, tax revenue.

taxation (noun)	tax income (noun)
the imposition of taxes; the practice of the government in levying taxes on the subjects of a state	government income due to taxation
charge against a citizen's person or property or activity for the support of government
government income due to taxation