amended return vs tax return

amended return and tax return both are nouns.

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

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

amended return: a tax return that corrects the information in an earlier return
tax return: document giving the tax collector information about the taxpayer's tax liability

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

amended return (noun)	tax return (noun)
a tax return that corrects the information in an earlier return	document giving the tax collector information about the taxpayer's tax liability