[dbuxton]

Well, there is such a word, certainly in the UK.

A more constructive comment might be, "the spelling variant you have used is normally a noun meaning 'a person who depends on another for their upkeep or care', where here you want the more normal adjectival spelling 'dependent'."

Although fwiw it seems that even as an adjective "dependant" might fly: http://www.wordnik.com/words/dependant