You can create a one time bill for a member through the Action menu in the bottom left hand corner of their profile.
Simply click on the Action menu link in the bottom left hand corner. Click on +Bill in the menu, then choose One Time Bill in the new popup menu.
On the Add a Bill screen, fill out the fields, then click on Save Changes to finish adding the bill.
After you save the bill, the system will take you to a screen where you can process the payment right away if necessary. If you plan on processing the bill at a later date, just navigate away from the screen. Later, when you are ready to process the bill, you can locate it by going to Financial> View All Bills on the member's profile.