The guest ledger is a balance sheet ledger account code that could contain two types of information. In the first place we have the revenue that is consumed by customers but has not been paid/charged yet. This will be stated debit on the ledger account. Secondly it could contain the pre payments of customers which would be stated credit. Sometimes these two things are separated to two different ledger account codes depending on the ways for the PMS to process and report this information.