This may be chiefly an ESL phenomenon, but confusion exists concerning the use of the adjective demandable.
My attention was drawn to the topic by this email:
I am an English teacher [from Turkmenistan]. I know English pretty well; however, I confuse the words “demanding” and “demandable.” Can you help me to distinguish those words? “He has a demandable character.” Or, “he has demanding character, or characteristics?”
The OED defines demandable as “That may be demanded or claimed.” Merriam-Webster defines it as “subject to being demanded.” Here are examples of the correct usage of demandable:
A bank at the time of levy was entitled under state law to set off against the balance in the delinquent taxpayer’s checking account only those debts owed to the bank by the taxpayer which were liquidated and demandable at the time of the levy.
But the BIR argued the tax debts have become “demandable… and collectible,” as [the debtor] has been ignoring a final assessment notice sent to him.
Judicial power includes the duty of courts of justice to settle actual controversies involving rights which are legally demandable and enforceable.

