Best answer by Endikebks
As this is your first post, welcome to the Pure Planet community!
Simple answer to your question - everybody who submits their meter readings any day other than the monthly anniversary of their first payment.
Technically it's not changed. Your reading should appear, then an estimate for the reading on the anniversary date.
If it worries you and you want to avoid it, send in your meter readings on your anniversary date, the date before your statement, and you will have no more estimates.
Hope that helps