allowable vs deductible

allowable is not a noun while deductible is a noun.

Word	Noun	Adjective	Verb	Adverb
allowable	No	Yes	No	No
deductible	Yes	Yes	No	No

allowable (noun)	deductible (noun)
	a clause in an insurance policy that relieves the insurer of responsibility to pay the initial loss up to a stated amount
	(taxes) an amount that can be deducted (especially for the purposes of calculating income tax)

allowable (adjective)	deductible (adjective)
that may be permitted especially as according to rule	acceptable as a deduction (especially as a tax deduction)
deserving to be allowed or considered
deductible according to the tax laws