Shortly before Christmas I found that I had a huge credit balance with my energy supplier, Spark Energy I contacted them for a refund of £1000 (which still left me with a fairly hefty credit balance, but having been stung in the past I would rather be cautious about it at least until the summer months). Their refund process takes a ludicrous 28 working days to complete, i am due to receive my refund some time next week. I received an email yesterday advising that they have had to reduce the refund amount to £720 "due to some incorrect meter readings which have now been removed". Checking my online account details, I can see that they have effectively credited every bill since March 2013 (all bar the first I had from them) and issued one whopping bill for little under £3k! All previous invoices have been completely removed so that I couldn't compare the new bill with the previous ones and figure out what they have done. I called them today and after much confusion eventually was told that my account was reviewed as part of the refund process and they noticed that there was a negative consumption of 409 units (which they estimated to be around £400) dating back to Nov/Dec 2013. I have lodged a complaint as the whole thing is very unclear and I am currently waiting for a call back from a Manager. I'm hoping someone can give me a bit of advice about where I stand with this and what my rights are. Am I right in thinking that this would fall within the back-billing principle and therefore since the error was beyond 12 months ago they cannot charge me? And if that is not the case, what are my rights in terms of the info they must provide? Surely they must be able to illustrate clearly the changes that have been made to my account?