annually vs every year

annually and every year both are adverbs.

Word	Noun	Adjective	Verb	Adverb
annually	No	No	No	Yes
every year	No	No	No	Yes

As adverbs, annually and every year are synonyms defined as:

Other synonyms of annually include each year, yearly.

annually (adverb)	every year (adverb)
without missing a year	without missing a year
by the year; every year (usually with reference to a sum of money paid or received)