markup vs mark up

markup is a noun but mark up is not a noun.

Word	Noun	Adjective	Verb	Adverb
markup	Yes	No	No	No
mark up	No	No	Yes	No

markup (noun)	mark up (noun)
detailed stylistic instructions for typesetting something that is to be printed; manual markup is usually written on the copy (e.g. underlining words that are to be set in italics)
the amount added to the cost to determine the asking price

markup (verb)	mark up (verb)
	increase the price of