This article only relates to the Legacy Event Module, which was replaced in 2013. Only use this article if you use the old Event Module.
If you have events for which people register who you do not want to have as actual profiles in your database, you can create a profile called 'Miscellaneous Event Sign Ups' (or whatever you like), and relate all of those 'anonymous' sign ups to this profile.
1. Go to Profiles > Create New Profile. Enter the Organization Name as 'Miscellaneous Event Sign Ups,' or whatever you prefer. All other contact info can be left blank.
2. Click Save. You do not need to create any related profiles or any other information, and the profile does not need to be set as a member.
3. Go to Admin > Set Preferences > Application Settings, and choose the Online Payments tab.
4. Click the Anonymous Profile ID browse button [...] to open the Profile Selector. Search for the profile that you just created in steps 1-2, and click Select.
5. Click Save at the bottom of the screen.
Now, in any event registration, you can assign this anonymous profile to a sign up (right-click, Look Up Profile ID) and the invoice will be created under that profile. You can also use the 'Assign Anonymous Profile' option when accepting online event registrations.