Why does our puppy goto toilet inside the house?

Our puppy is 9 weeks old and we have had him for just over 1 week. We are toilet training him by taking him outside into the garden regularly on a lead and saying "toilet" and then waiting for him to go before chanting the command over and over. A treat is then immediately given and lots of praise. However i do expect accidents inside the house but recently we have been taking him outside and he doesnt seem interested in going to toilet, then as soon as you cross the threshold into the house he will then goto toilet. He doesnt even seem to care where he does it, even on his bed in his crate, day or night. We have a spray to remove the odour and deter him from repeating the accident in the same spot. He does seem very excited being a puppy, but i dont understand why he seems to wait until indoors to go, any ideas people?