You should be regularly checking every aspect of your energy bills each time you receive one. This is especially important if your electricity profile has been, or will be, upgraded under the P272 scheme and you are new to this type of billing.
Anyone with a half hourly electricity supply will have an Available Supply Capacity (ASC) charge on their invoice each month. We recommend that you keep checking this amount as it should not change from bill to bill, unless you or the network operator changes it.
When speaking with one of our customers who had recently changed their Supplier, we discovered that three of their sites had had their ASC increased, a mistake which would have cost them around £1,200! The Supplier quickly rectified the issue and refunded the money, but it just goes to show that you should check every part of your bill regularly.
Larger gas supplies could also experience a similar situation: it is termed Supply Offtake Quantity (SOQ) instead, and more information on that can be found here.
Of course, we are here to help, so you could always contract us to do this checking for you under our account management service.