write off vs write down

write off and write down both are verbs.

Word	Noun	Adjective	Verb	Adverb
write off	No	No	Yes	No
write down	No	No	Yes	No

As verbs, write off and write down are synonyms defined as:

Other synonyms of write off include expense.

write off (verb)	write down (verb)
reduce the estimated value of something	reduce the estimated value of something
concede the loss or worthlessness of something or somebody	put down in writing; of texts, musical compositions, etc.
write something fluently, and without hesitation
cancel (a debt)