Answer:
The tax information interview is valid for a period covering the year signed plus 3 additional calendar years. The notification to retake the tax interview is sent in order to make sure developers are aware and have the opportunity to renew your tax information prior to expiration.
If you would like to maintain monetizing and Mobile Ads on the Amazon Appstore with accurate Tax information (to sell paid apps / in-app purchasing, or use of Amazon Mobile Ads) you will need to retake the Royalty Tax Identity Interview (for apps / in-app purchase) and Service Tax Identity Interview (for Mobile Ads) before it expires.
To retake your company's Tax Identity Interview, please sign into your company's developer account as an administrator and go to "Settings" > "Tax Identity".
