Refactoring a series of if-return statements.
It seems that you are wanting your Check enum to be able to provide a little more information for you without the messiness of the if-then clutter. What about combining the status strings with the enumerator? Something like:  

public class CheckStatus{
    public static readonly CheckStatus 
      IsSuccessful = new CheckStatus { Value = "Approved" },
      AreClarificationsSent = new CheckStatus { Value = "Clarifications" },
      IsInProgress = new CheckStatus { Value = "Check in progress" },
      IsTemplateSent = new CheckStatus { Value = "Sent" },
      IsReceived = new CheckStatus { Value = "Received" },
      NotReceived  = new CheckStatus { Value = "Not Received" };

    private CheckStatus() { }
    public string Value{ get; private set; }
}


Very easy to maintain and puts the minor implementation details behind the purpose of the Check enumerator. Provides much the same benefit of an enumeration. I would have liked to make this a struct, but I would not (without going into IL) have a parameterless private ctor.