Most people find that the electricity statement is usually very prompt and timely. Certainly I submit my readings and the statement is always available same day. I don't have gas myself, but oftentimes gas customers sometimes have a slight delay as they have to apply volume adjustments and calorific value tweaks to 'provisional' bills.
I suspect that the Next Drive tariffs are still somewhat in 'beta' so it may take a bit more shuffling around in the back end to make sure the correct ToU data is not only applied to the billing, but the data parsed to the template that generates the PDF statement is both accurate and covers all the bases. Now, if I was the developer at the back end, I would have already had the software sandboxed, tested and debugged before going from 'beta' to 'production', but I'm guessing that the reverse happened. They rolled out the tariff and the tech bods are trying to make the magic happen after the fact. It is often thus, in many industries. I've been guilty of it myself in the past. I could be wrong, but I know the game only too well to know that these things happen.
Don't shoot me, I'm only the piano player. I DON'T work for or on behalf of EON.Next, but am willing to try and help if I can. Not on mains gas, mobile network or mains drainage. House heated almost entirely by baby dragons.