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If you are manually creating the document, you can fill this tab from one or more documents selected as the basis.
Note. For tax invoice with the Sale or Other transaction type, the list on the tab is populated from the basis document and is not editable. 
The "Tax Invoice (create)" form. The Inventory and Services tab
For tax invoice with the Advance transaction type, the item list is populated from the customer order if order is the basis and from a payment if payment is the basis. In such cases, editing of the list is possible.
To add a line to the document, click the Add button and either select the item from the Items catalog in the Item column or specify the transaction contents (the Content column).
You can specify some additional properties of an inventory item (such as size, color etc.) or service in the Characteristic column if the Enable Item Characteristics option is selected on the Administration > Settings: Purchasing and Warehouses form. Also, you can specify the batch (lot) number for items in the Batch column if the Enable batches option is selected on the same form. To learn more about the item settings, see Settings: Purchasing and Warehouses.
In the Quantity column, you can specify the item quantity.
In the Unit column, you can specify a UOM for the item if the Multiple UOMs per Item option is selected on the Administration > Settings: Purchasing and Warehouses form.
The Price column is filled in automatically from the appropriate price list if such price is available (see Setting Item Prices). You can change the price manually if you have appropriate rights. If the contract is in a foreign currency, the Currency and Price (Curr.) columns are also available.
For documents with the Advance transaction type, the Contract, Currency, Exchange Rate, and Purchase Order columns appear.
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