Why change the name?
When sending out P11D benefit statements (or facsimiles) via email, or when saving files as PDFs, you may want to change the naming scheme that is applied, this could be for preference or more practical reasons, e.g. you use the employee's payroll number to password protect the file, it would therefore defeat the object to have this visible in the file name. There are various options to choose from. To change the naming convention, click on the employer icon: 
Then in the left hand pane, click company settings and edit:
You can now select the drop down list under Naming convention for file output, here is where you can choose how you want the P11D benefit statement files to be named. NOTE: You will notice all schemes have an ID_2, please ignore this as this is an internal reference to prevent duplication.
Now simply choose you scheme from the dropdown list and press OK:
With the one I have selected, an example benefit statement name would look like the below:
And that's it, it is worth noting you will only see these file name changes when producing multiple files (not singular) or when sending the benefit statement via email (which can be singular).