subtract vs carry back

subtract and carry back both are verbs.

Word	Noun	Adjective	Verb	Adverb
subtract	No	No	Yes	No
carry back	No	No	Yes	No

As verbs, carry back is a hyponym of subtract; that is, carry back is a word with a more specific, narrower meaning than subtract:

subtract: make a subtraction
carry back: deduct a loss or an unused credit from taxable income for a prior period

subtract (verb)	carry back (verb)
take off or away	deduct a loss or an unused credit from taxable income for a prior period
make a subtraction