You can check and enable the settings for this by completing the following steps:
Note that in Access Capture the edit button is represented by a pencil icon.
Log into Capture using an Administrator Account (this will open the Readsoft Online Control Center)
Select Services, Extraction from the left hand side
In the Document type screen, select the Edit button, followed by the Configuration option to the right of the enabled document types (those that are ticked).
Select the Rules tab
Ensure Duplicate Invoice Check is ticked
Select the Fields tab
Select the Edit icon to the right of the InvoiceNumber item
Select the Enforce validation setting
Select OK
Select OK again on the Document Type screen to save your settings
You now need to further configure this for each of your buyers and document types (the settings in the above steps will only apply for new buyers - and will not apply for existing ones).
Select the Buyers item to the left hand side
Select one of your Buyers
Select the Extraction tab followed by the Edit icon
Select Configuration to the right of one of the entries in Country and Type
Select the Edit icon to the right of the InvoiceNumber item
Select the Enforce validation setting
Select OK
Select OK again on the Document Type screen to save your settings
Continue adding the Enforce validation setting on each of your document types
Note - if you have multiple buyers, you will need to enable the setting on each document type for each of your buyers.