We are calculating the delay interest based on the delay interest scheme 
set out in the electricity supply standard policy and charging to customers 
who pays the electricity bill after the due date. We are invoicing the 
delay interest together with the next bill. This time, we identified 
incorrect delay interest for part of the customers' electricity bills for 
June 2011.

We are invoicing a photovoltaic generation surcharge from April 2011 (JPY 
0.03/kWh for FY 2011). This must have been excluded from the basis in 
calculating the delay interest. Because of incorrect calculation in the 
software, we incorrectly calculated the delay interest including this from 
April 2011. The number of customers affected was approx 9,300 and the 
total amount was approx JPY 11,000 (JPY 1 for each customer).

We deeply apologize for causing great inconvenience to customers. As for 
customers affected, we will reconcile the difference at the next 
electricity bill (July 2011). 

As to the incorrect calculation in the software, we fixed the matter and 
are checking that the matter is properly solved. From now on, in order to 
avoid repeating similar matter, we will endeavor to ensure correct 
processing.

If you have any query, we would be grateful if you could contact our 
Customer Support. 

https://www.tepco.co.jp/en/customer/support/top-e.html

*delay interest scheme means, if a customer does not pay a bill by the 
due date for payment which is on the thirtieth date counted from the next 
date of measurement. The delay interest rate is 10% per annum and the 
amount of delay interest pro rated by the duration between the date of 
payment and the next date of measurement. Principally we invoice the delay 
interest together with the next electricity bill.