The AWS Billing Conductor computation flexes to the changes that you make in a given month, while retaining the historical integrity of your prior period billing data. This is best described with an example:
In this example, we have two billing groups, A & B. Billing group A starts the billing period with accounts 1-3 in the group. At the mid-month point, the payer account moves Account 3 to billing group B. At that point, the re-computation of the costs for billing groups A & B are required to accurately model the latest change. When Account 3 is moved, billing group A’s usage is modeled as if Account 3 was not a part of the billing group during the current billing period. Additionally, billing group B’s usage is modeled as if Account 3 was a part of billing group B since the beginning of the billing period. This approach eliminates the need to calculate complex rates and chargeback models when accounts move across groups within the billing period.
Billing Group A            Days: 1-15        Days: 16-30        EOM         Account 1$ 100$ 100$ 200 Account 2$ 100$ 100$ 200 Account 3$ 100N/AN/A Total$ 300$ 200$ 400
Billing Group B            Days: 1-15        Days: 16-30        EOM         Account 4$ 100$ 100$ 200 Account 5$ 100$ 100$ 200 Account 6$ 100$ 100$ 200 Account 3$ 100$ 100$ 200 Total$ 400$ 400$ 800