joint return vs tax return

joint return and tax return both are nouns.

Word	Noun	Adjective	Verb	Adverb
joint return	Yes	No	No	No
tax return	Yes	No	No	No

As nouns, tax return is a hypernym of joint return; that is, tax return is a word with a broader meaning than joint return:

joint return: a return filed by a husband and wife
tax return: document giving the tax collector information about the taxpayer's tax liability

Other hypernyms of joint return include income tax return, return.

joint return (noun)	tax return (noun)
a return filed by a husband and wife	document giving the tax collector information about the taxpayer's tax liability