Is not allowable proper English?
Yes, the term 'not allowable' is correct in English.The word 'allowable' is an adjective, a word that describes a noun: an allowable expense, an allowable activity, etc.The word 'not' is an adverb that can be used to modify the adjective allowable, for example:The gas is an allowable expense but the sandwich is not allowable.It is not allowable to make personal calls while at the front desk.