From Longman Dictionary of Contemporary Englishwrite something ↔ down phrasal verb1WRITEto write something on a piece of paperThis is the address. Do you want to write it down?2to officially say that a debt no longer has to be paid, or officially accept that you cannot get back money you have spent or lost syn write off →write→ See Verb table
Examples from the Corpus
write down• Children must be given the opportunity to talk through their ideas before they are expected to write them down.• Of course it's much easier to demonstratetechniques than write them down.• She asks me if I have written it down.• That man seemed to know every chorus that had ever been written.• What do you do if you have a child who already knows the pattern and they just write it down?• He watches Manny stare angrily at Allen, who is writing things down in a notebook.• No, don't you go writing things down, or you're out on your ear.From Longman Business Dictionarywrite something → down phrasal verb [transitive]ACCOUNTING to reduce the value of an asset as shown in a company’s accountsThe giant hospital chain said it will write down about $100 million in assets and reserves. → see alsowrite-down →write→ See Verb tablewrite-downˈwrite-down (also writedown) noun [countable, uncountable]ACCOUNTINGwhen the value of an asset as shown in a company’s accounts is reducedThe charge includes $2.7 million from the write-down of assets.