pay off vs pay back

pay off and pay back both are verbs.

Word	Noun	Adjective	Verb	Adverb
pay off	No	No	Yes	No
pay back	No	No	Yes	No

As verbs, pay off and pay back are synonyms defined as:

Other synonyms of pay off include fix, get.

pay off (verb)	pay back (verb)
take vengeance on or get even	take vengeance on or get even
eliminate by paying off (debts)	act or give recompense in recognition of someone's behavior or actions
pay someone with influence in order to receive a favor
yield a profit or result
pay off (loans or promissory notes)
do or give something to somebody in return