taxomate can import data as far back as Amazon will allow through its API. This may or may not be a complete history of all of your settlements.
To check in Amazon Seller Central go to Reports > Payments > All Statements
Request statement reports be generated if possible. Once the reports are generated these statements can be downloaded into taxomate.
Please note: If no statements are imported into taxomate after a few hours you may have to reach out to Amazon Seller support to request your settlements be converted to Settlement Version 2 (Flat V2).