# Design

The Account ES SII Module introduces the following concepts:

## SII Invoice

The main concept introduced by the Account ES SII Module is the SII Invoice. It relates a Invoice <account_invoice:model-account.invoice> with it state in the SII. A record is automatically created when an invoices that should be sent to SII is posted.

When the invoice is correctly set it stores the secure validation code of the delivery. If there are any error with the invoice, the error code and description are stored.

See also

The SSI Invoices can be found by opening the main menu item:

> Financial ‣ Invoices ‣ SII Invoices