diff --git a/pkg/errors/errors.go b/pkg/errors/errors.go
index ad0a524..dc1f584 100644
--- a/pkg/errors/errors.go
+++ b/pkg/errors/errors.go
@@ -44,6 +44,8 @@ var (
 	ValErrParentIDNotSet       = errors.New("Parent Membership ID not provided")
 	ValErrParentIDNotFound     = errors.New("Parent Membership ID not found")
 	ErrSubscriptionNotFound    = errors.New("Subscription Model not found")
+	ErrSubscriptionInUse       = errors.New("This subscription is in active use by existing members.")
+	ErrInvalidSubscriptionData = errors.New("Provided subscription data is invalid. Immutable fields where changed.")
 )
 
 var Responses = struct {