Custom properties

I am trying to create an account using the resource /v1/accounts but I am getting and error

  "reasons": [
      "message""Missing required valueSmiley SadSubscription's Commissionable)"
I am told that this error is because of a custom property 'Commision__c'. Being new to Zuora and new to this environment I am not sure how I see where this custom property is defined and how to see what a valid value would be (type, value, etc.). Ideas?