Greetings,

I'm having some trouble with a trigger I've written.  This is intended to create a task based upon certain fields in a custom object.  The tasks are created as expected, except WhatID is not populated in the tasks, therefore they are not linked to the custom object record.
 

/**********************************************************************

  This trigger checks if tax docs are received and/or scanned on
  Tax_Services__c object and assigns tasks accordingly.

**********************************************************************/

trigger Tax_Docs on Tax_Services__c (before insert, before update) {

    List <Task> TasksToCreate = new List <Task> ();

    for(Tax_Services__c e : Trigger.new)
    {
  
        if(Trigger.isUpdate)
        {
            Tax_Services__c oldService = Trigger.oldMap.get(e.ID);
            
            if(e.Tax_Docs_Received__c == TRUE && e.Tax_Docs_Scanned__c == TRUE)
            {
                if(e.Tax_Docs_Received__c != oldService.Tax_Docs_Received__c || e.Tax_Docs_Scanned__c != oldService.Tax_Docs_Scanned__c)
                {
                    TasksToCreate.add(new Task(OwnerID = e.Tax_Advisor__c,
                                               Subject = 'Tax Docs Received and Scanned',
                                               WhatID = e.Id,
                                               ActivityDate = date.today(),
                                               Status = 'Not Started',
                                               Priority = 'Normal',
                                               Hidden__c = 'Tax Docs Received & Scanned'));
                }
            }
            
            if(e.Tax_Docs_Received__c == TRUE && e.Tax_Docs_Scanned__c == FALSE)
            {
                if(e.Tax_Docs_Received__c != oldService.Tax_Docs_Received__c || e.Tax_Docs_Scanned__c != oldService.Tax_Docs_Scanned__c)
                {
                    TasksToCreate.add(new Task(OwnerID = e.Tax_Advisor__c,
                                               Subject = 'Scan Tax Docs',
                                               WhatID = e.Id,
                                               ActivityDate = date.today(),
                                               Status = 'Not Started',
                                               Priority = 'Normal',
                                               Hidden__c = 'Scan Tax Docs'));
                }
            }
        }
    
    
        if(Trigger.isInsert)
        {
            if(e.Tax_Docs_Received__c == TRUE && e.Tax_Docs_Scanned__c == TRUE)
            {
                    TasksToCreate.add(new Task(OwnerID = e.Tax_Advisor__c,
                                               Subject = 'Tax Docs Received and Scanned',
                                               WhatID = e.Id,
                                               ActivityDate = date.today(),
                                               Status = 'Not Started',
                                               Priority = 'Normal',
                                               Hidden__c = 'Tax Docs Received & Scanned'));
            }
            
            if(e.Tax_Docs_Received__c == TRUE && e.Tax_Docs_Scanned__c == FALSE)
            {
                    TasksToCreate.add(new Task(OwnerID = e.Tax_Advisor__c,
                                               Subject = 'Scan Tax Docs',
                                               WhatID = e.Id,
                                               ActivityDate = date.today(),
                                               Status = 'Not Started',
                                               Priority = 'Normal',
                                               Hidden__c = 'Scan Tax Docs'));
            }
        }
    }
            try
            {
                Insert TasksToCreate;
            }
            catch (System.DmlException ex)
            {
                System.Debug (ex);
            }
}

Any thoughts on what may be happening here?