Your receipts include incorrect or incomplete information or you wish to customize them. From where is this information being drawn and how can you update it?
The Account Profile should reflect your organization's data as you wish to present it on your website and email confirmations. Account Profiles are broken into two parts, the Administrator or My Profile, and the Organization Profile. These profiles can be accessed through the Account link In the upper right corner of the Dashboard. See this article on how to update this information.
If you wish to add a note to the receipts, there are three options: Check Order Note, Credit Card Order Note, and Confirmation Message. See this article for adding receipt notes.
See also this article for updating the receipt header.