Hi Folks, 

I do receive "Duplicate Id in List" error when I run the code. Please could you revew and advise what is wrong and what can be improved here ?  Duplicate Id was found in  list "acctaddresstoupdate ".   Many Thanks in advance. 

global Database.QueryLocator start(Database.BatchableContext BC) {
       return Database.getQueryLocator([Select id, BDF_Target__c, OCE__PreferredAddress__c, OCE__PreferredAddress__r.BDF_Visited__c from OCE__AccountTerritoryFields__c where OCE__PreferredAddress__c != null]);
                         
    }

    global void execute(Database.BatchableContext BC, List<OCE__AccountTerritoryFields__c> scope) { system.debug(scope);
     
        list<OCE__AccountAddress__c> acctaddresstoupdate = new  list<OCE__AccountAddress__c> ();
        map<id,OCE__AccountAddress__c> Acctaddnodupes = new map <id,OCE__AccountAddress__c>();
       
            for(OCE__AccountTerritoryFields__c acctterfields : [Select id, BDF_Target__c, OCE__PreferredAddress__c, OCE__PreferredAddress__r.BDF_Visited__c from OCE__AccountTerritoryFields__c where id IN :scope]) {
                system.debug(acctterfields); 
                 acctaddresstoupdate.add(acctterfields.OCE__PreferredAddress__r); 
 
                if(acctterfields.BDF_Target__c == 'Yes') {
                    system.debug('Completed');
                    acctterfields.OCE__PreferredAddress__r.BDF_Visited__c = true;
                    update acctaddresstoupdate;
                    system.debug(acctaddresstoupdate);

                } 
                  else {
                     system.debug('Not Completed');
                     acctterfields.OCE__PreferredAddress__r.BDF_Visited__c = false;
                     update acctaddresstoupdate;
                     system.debug(acctaddresstoupdate);
                     
                } 
     
                }
                map<id,OCE__AccountAddress__c> AcctAddmap = new map <id,OCE__AccountAddress__c>();
                AcctAddmap.putAll(acctaddresstoupdate); 
                if(AcctAddmap.size()>0){
                update AcctAddmap.values();
              
                                    }

    }