From LaneWiki

“This Company” Customer Record

The system uses a customer record that represents the business itself. The customer id of this record is saved in SysString:company-customer-id (by default, the installer uses the id “%%me%%�?). This record is used by various tools, including the default reports. The taxes and terms of this customer should be the same as a regular customer. In the US, this customer can be used for Use Tax calculation (when a company uses something itself which was bought for resale and thus tax-exempt).