...
In the Entity field, select an entity of your company for which this document is being prepared. The Entity field is available if the Multi-Company Accounting option is selected on: Administration > Settings > General Settings. You can select your personal default entity to appear in documents; for this, refer to Personal Settings. If you have not selected your default entity, the entity defined first will be used as the system default value.
...
The Customer Order field is filled in automatically if the credit note is linked to it. You can link the credit note to a customer order manually; for this, click the arrow button in the field, then click Show all. The list of customer orders appears; only the orders for the same contract are shown in the list. If you need to return items linked to different orders, you can move the Customer Order field from the Main tab as a column to the table on the Inventory tab. For this, use the Settings button on the toolbar (for more information, see Document Toolbar).
If this credit note was not generated for a specific invoice, in the Basis box select the invoice which is being corrected or adjusted by this credit note. Once the basis document is selected, the data is copied to this note. If, after you edited this credit note you want to cancel the changes and reset to the initial details, use the Fill in ( 
) button – the details from the basis document will be copied to the credit note.
The Warehouse field is required, if the Multiple warehouses option is selected on the Administration > Settings > Purchasing and Warehouses form.
In the Warehouse box, in case of return, you can select the warehouse to which the goods will be returned. If you need to return items to different warehouses, you can move the Warehouse field from the Main tab as a column to the table on the Inventory tab. For this, use the Settings button on the toolbar (for more information, see see Document Toolbar).
The Project field is available if the Project Management functionality is turned on on the Administration > Settings > General Settings. You can link a credit note with a project from the list of available projects. If the items in this credit note are associated with different projects and you need to specify different projects for different items, you can move the Project field from the Main tab as a column to the table on the Inventory and Services tab. For this, use the Settings button on the toolbar (for more information, see see Document Toolbar).
You can use the Comment text box to provide any relevant information on this transaction.
Notice the hyperlink below the Warehouse field–on the screenshot above, AED* VAT Applied* Prices include VAT (can be different in your document) – by clicking the hyperlink, you open The Prices and Currency dialog box and can view the price-related and tax-related settings for the credit note. The settings can be change only if the credit not is not based on an invoice.
...
For descriptions of other buttons, see see Document Toolbar.