While exporting expenses from Gorilla Expense into Accounting system, you may get an error with the following message "Object reference not set to an instance of an object" as shown in the image below. To resolve this do the following-
1) Edit and save all transactions on the report 
2) Make sure Pay Method is assigned to all transactions in a report. If it is not, please email support@gorillaexpense.com, if you are hosting Gorilla Expense on the cloud. 
3) If you are hosting Gorilla Expense On-Premise, please provide the following solution to your IT / partner or email support@gorillaexpense.com
Open TblExpenseDetails table in the database in edit mode and search for all expenses with expenseid = "ReportID" using this where clause "where expenseid = xxx". For example, in the screen below the reportid is 303 (associated with confirmation number GE303). Assign the pay method to any transactions missing pay method.