An user Story is a {small} functionality which can be tested and
delivered within a timebox. Scenarios represent different ways of interacting
with that functionality. So, an User Story may have multiple scenarios.
Scenarios are implemented in {re-usable} steps.
In your case, the various scenarios could be
Feature: Invoice duplication
...
Scenario: Valid invoice
...
Scenario: Non-existing invoice
...
Scenario: Already duplicated invoice
...
Scenario: Expired invoice
...
The scenarios above verify/test your User Story/Feature i.e. Invoice Duplication.
Scrum Guide => https://www.scrum.org/Portals/0/Documents/Scrum%20Guides/2013/Scrum-Guide.pdf#zoom=100