I can’t recall ever having used the adjective contractual, meaning “of, pertaining to, or secured by a contract.” I find it an awkward mouthful.
As a general matter, I’d rather simply use contract, as in contract terms and contract obligations rather than contractual terms and contractual obligations.
And rather than referring to contractual instruments or contractual arrangements, why not just say contracts?
Nevertheless, contractual occurs frequently in contracts. (Sometimes it’s misspelled contractural, with an extra r.) For example, it occurred in 1,182 contracts filed as exhibit 10 “material contracts” on the SEC’s EDGAR system in the past month. I particularly enjoyed its use in the following bit of nonsense:
Terms of this agreement are contractual and not a mere recital.