When you switch to us, we ask for an opening meter reading to send to your old supplier so they can close your account and issue a final bill. On the way over, your reading goes through a series of third–party checks to ensure your old supplier agrees with it.
Sometimes, your old supplier might tell you we haven't sent them the reading. This is normally because the readings are still being checked, or your old supplier has yet to agree them (often unknown to call centre staff).
Since your old supplier is responsible for releasing your final bill, we can't say for certain when you'll get it, but from our experience it usually happens in four to six weeks.