Effective billing date, account activity, and volume discounts
When the member account owner accepts your request to join the organization, you immediately become responsible for the member account's charges. If the member account joins in the middle of the month, the management account is billed only for the latter part of the month.
For example, if a member account joins an organization on March 10, then Amazon bills the management account for the member account’s period of usage starting on March 10. The member account's original owner is still billed for the first part of the month.
Billing and account activity
Each month, Amazon charges the management account owner, and not the owners of the member accounts. To see the total usage and charges across all the accounts in an organization, see the Bills page of the management account. Amazon updates the page multiple times each day. Additionally, Amazon makes a downloadable cost report available each day.
Although the owners of the member accounts aren't charged, they can still see their usage and charges by going to their Amazon Bills pages. They can't view or obtain data for the management account or any other member accounts on the bill.
Volume discounts
For billing purposes, Amazon treats all of the accounts in the organization as if they were one account. Some services, such as Amazon Data Transfer and Amazon S3, have volume pricing tiers across certain usage dimensions that give you lower prices the more you use the service. With consolidated billing, Amazon combines the usage from all accounts to determine which volume pricing tiers to apply, giving you a lower overall price whenever possible. Amazon then allocates each member account a portion of the overall volume discount based on the account's usage.
For example, let's say that Bob's consolidated bill includes both Bob's own account and Susan's account. Bob's account is the management account, so he pays the charges for both himself and Susan.
Bob transfers 8 TB of data during the month and Susan transfers 4 TB.
For the purposes of this example, Amazon charges $0.17 per GB for the first 10 TB of data transferred and $0.13 for the next 40 TB. This translates into $174.08 per TB (= .17*1024) for the first 10 TB, and $133.12 per TB (= .13*1024) for the next 40 TB. Remember that 1 TB = 1024 GB.
For the 12 TB that Bob and Susan used, Bob's management account is charged ($174.08 * 10 TB) + ($133.12 * 2 TB) = $1740.80 + $266.24 = $2,007.04.
Without the benefit of tiering across the consolidated bill, Amazon would have charged Bob and Susan each $174.08 per TB for their usage, for a total of $2,088.96.
To learn more about pricing, see Amazon
Pricing
Amazon Free Tier for Amazon Organizations
For services such as Amazon EC2 that support a free tier, Amazon applies the free tier to the total usage across all accounts in an Amazon organization. Amazon doesn't apply the free tier to each account individually.
Amazon provides budgets that track whether you exceed the free tier limits or are forecasted to go over the free tier limits. Free tier budgets are not enabled for organizations by default. Management account can opt in to free tier usage alerts through the Billing and Cost Management console. Free tier usage alerts aren't available to individual member accounts.
For more information about free tiers, see Amazon Free Usage Tier FAQs