As part of this agreement, at the mid-year point on an annual direct debit arrangement, the supplier will ask the customer for an actual meter reading if necessary and once they have received it, they will review the direct debit and change it to make it as accurate as possible for the remainder of the year to avoid a large build-up of credit or debit on their account. Alternatively, the money can be rolled over to take off the next bill if the customer prefers.