If you are on the Pro Plan or higher, then you can adjust the affiliate information on an existing transaction.
First, go to the Manage Transactions screen for any member and then click the edit icon 
on the appropriate transaction. A pop up window will be displayed where you can specify the affiliate and sub-affiliate ID for the transaction. If the transaction is associated with a subscription then changing the affiliate info will be applied to the current transaction and all future rebills on the subscription.
Click the Save button to save your changes.
Once you've changed the affiliate info on a transaction you'll be given the opportunity to send a commission request to the affiliate provider you're integrated with by clicking the 
icon in the Actions column. This option is only available when you're integrated with an affiliate provider that supports commission tracking.
Note: if the edit icon is greyed out it means that you are not on on the Pro Plan or higher.