Best answer by stephenrand
First post - welcome to the Pure Planet community!
When you join Pure Planet you will be asked for your initial meter readings just before the switch is complete, i.e. 16-17 days after you initiate the switch.
So you can aim to get it right by counting back the days. If you are a day or two out, don't worry. Send in the readings the day you move in, and at least make sure you take photos of the meters just to ensure you don't have any problems down the line.
Hope that helps. Enjoy your new home!