Free tier with AWS Organization

The AWS Free Tier is available to all types of customers – students, entrepreneurs, small businesses, and Fortune 500 companies are all welcome to sign up. If you are linked to an Organization (under AWS Organizations), only one account within the organization can benefit from the Free Tier offers. To calculate the Organization’s use of AWS Services under any Offers, AWS will aggregate the usage across all accounts in the Organization. You will be charged standard rates for use of AWS Services if AWS determine that you are not eligible for the Free Tier or have exceeded the limits for a particular service.

When it comes to the AWS Free Tier and AWS Organizations, there are a few important points to consider:

1. You are correct that the AWS Free Tier does not apply individually to each account within an AWS Organization. Instead, AWS applies the Free Tier benefits to the total usage across all accounts in the organization.

2. If an account leaves an AWS Organization, it will not regain its individual Free Tier benefits. The Free Tier period is tied to the initial 12 months after an account is activated, and this period cannot be extended or restarted.

3. Once an account has been part of an organization, even if it leaves, it will not get a new 12-month Free Tier period. After the initial 12 months from account activation, all resources on the account are billed at the standard, pay-as-you-go service rates.

4. It's worth noting that while the 12-month Free Tier benefits cannot be extended, AWS does offer some services with "Always Free" tiers or separate trial periods that can still be utilized even after the initial Free Tier period expires.

5. For organizations, the management account can opt in to receive Free Tier usage alerts through the Billing and Cost Management console, but these alerts are not available to individual member accounts.

In summary, leaving an AWS Organization will not reactivate or extend Free Tier benefits for an individual account. The Free Tier period is a one-time offer tied to the account's activation date, regardless of its organizational status.
Sources
Understand when AWS Free Tier starts and expires | AWS re:Post
Effective billing date, account activity, and volume discounts - AWS Billing
Extend AWS Free Tier benefits | AWS re:Post