The nominal accounting codes are stored within the Assignment in the Accounting Interface field under the Categories Tab. These nominal codes will be used in the export reports:
Your site can be set with a default Accounting Interface string so that every time a new assignment is created (or imported) it will pick up the default. The format is comma delimited and is structured like this - [sales nominal],[purchase nominal],[department/cost centre] - so with the example above 4001 is the Sales Invoice nominal with 5001 being the Purchase Invoice nominal and the cost centre/department is not in use.
This arrangement is a typical one that suits most accounts exports but some exports are more sophisticated and can take their nominal coding from other areas of the system, such as Branches and Sectors as well as Consultants, so it really depends on which system you are exporting to as to which arrangement suits your process. Generally if you are using an off-the shelf export on Etz, such as Sage or Xero, the Accounting Interface field, if used, will supply the coding to your accounts system.