Potty Training Issues

Question
I have a 6 month male miniature Cocker. We have had him for almost two months now. We create the puppy during the night but I let him out during the day with me. He usually goes to the bathroom outside when we take him which is on a very regular basis. He will run to the door if he doesn't have to go. We also praise him  and reward him when he goes outside. The problem is, when he does have to go while inside, he will go to the back door and relieve himself without letting us know. When we find it he knows he has done wrong by the tone of our voices and will hide. He knows how to get back inside the house by scratching or barking at the backdoor. I am at a loss as to what to do Thanks for any insight.

Answer
If he goes to theback door, and you don't let him out, it is your fault, a neglect, not an accident.  This might be a good case to use the bells many people are successful.  Hang some bells low on the outside edge of the door.  When he bats the door to go out, it will ring the bell bringing you on the run to open it.  

When you are around you need to keep a close eye on the dog.  Use closed doors or gates to keep it in the same room as you are, and perhaps as I do, a short chain fastened to the computer desk.  If you catch it in the act, give it a sharp ''Ah, ah, ah!'' and take it out.  When you can't watch it, crate it.