cost ledger vs book of account

cost ledger and book of account both are nouns.

Word	Noun	Adjective	Verb	Adverb
cost ledger	Yes	No	No	No
book of account	Yes	No	No	No

As nouns, book of account is a hypernym of cost ledger; that is, book of account is a word with a broader meaning than cost ledger:

cost ledger: ledger showing the accumulated costs classified in various ways
book of account: a record in which commercial accounts are recorded

Other hypernyms of cost ledger include account book, book, ledger, leger.

cost ledger (noun)	book of account (noun)
ledger showing the accumulated costs classified in various ways	a record in which commercial accounts are recorded