In the Chart of Accounts module you can either create accounts manually or import them from another software (e.g. DATEV). You can also customize existing charts of accounts.
The default accounts for the financial accounting export of receipts are located in the basic settings in the "Tax/Currency" area and in the settings per project.
If settings have been made on a per-project basis, these will be preferred over those from the global basic settings.
You can find more information in our manual: