Square sellers use the Seller Dashboard to manage and monitor business activities for their accounts. These activities result from actions made using Square products and calls to Square APIs. Square also hosts a Sandbox Seller Dashboard where developers can see the results of API calls made from their applications in the Sandbox.
Verify the payment in the Sandbox Seller Dashboard
On the Sandbox test accounts page in the Developer Dashboard, choose Square Dashboard next to Default Test Account. This link opens the Sandbox Seller Dashboard associated with the default test account.
In the Sandbox Seller Dashboard, choose Transactions.
On the Transactions page, choose the payment you made. If you don't see your payment, select a date range that includes your payment.