How can I preview the available invoice formats in Billing?

1. Select Tools, Invoice Formats.
2. Select the Billing Type.
3. From the Invoice Format list, select the format you wish to preview.
4. Click Preview.

 NOTE: If you change the Design name: to preview other formats and then click Close, it will save the change to the new format. Click Cancel to revert the selection to the original design.  

How do I determine which format I am using for my invoice in Billing?