exempt vs let off

exempt is an adjective but let off is not an adjective.

Word	Noun	Adjective	Verb	Adverb
exempt	No	Yes	Yes	No
let off	No	No	Yes	No

As verbs, exempt and let off are synonyms defined as:

Other synonyms of exempt include excuse, relieve.

exempt (adjective)	let off (adjective)
(of persons) freed from or not subject to an obligation or liability (as e.g. taxes) to which others or other things are subject
(of goods or funds) not subject to taxation

exempt (verb)	let off (verb)
grant exemption or release to	grant exemption or release to
grant relief or an exemption from a rule or requirement to