The API login ID and transaction key are authentication values used to identify your account when connecting a website or application to the Authorize.Net payment gateway for transaction processing. The API login ID and transaction key cannot be used to log into the Merchant Interface.
The API login ID has eight to twenty-five alphanumeric characters. The transaction key has sixteen alphanumeric characters.
To obtain the transaction key:
1. For sandbox API requests, log into the sandbox Merchant Interface at https://sandbox.authorize.net. For production API requests, log into the production Merchant Interface at https://account.authorize.net.
2. Navigate to Account > Settings > API Credentials & Keys.
3. Click New Transaction Key.
4. Click Submit.
5. Request and verify a PIN in order to see the transaction key.
Yes you can process normal refunds and also submit unlinked refunds on your sandbox account using ECC. Expanded Credit Capabilities (ECC) allows you to issue refunds on transactions more than 120 days old, and issue refunds for transactions that were not processed through your Authorize.Net account. It is enabled automatically on sandbox accounts. ECC is a free feature, but please note that for live accounts, ECC is subject to approval. The account owner or administrator will need to fill out a form to enable this service.
Solution IDs uniquely identify the software source of transactions. Software vendors can create and manage solution IDs within the Reseller Interface and include it in transaction request API calls. Solution IDs may be used by any Authorize.Net merchant using the software.
To use Solution IDs to identify the software source of transactions, see the Solution ID Integration Guide.
The sandbox is for integration testing only and should not be used for load or stress testing. We may suspend sandbox accounts that send unusually high transaction volumes.