You are never charged for a duplicate.
What counts as a duplicate
A duplicate is the same person captured again. If the same name and company are scanned a second time, that scan is not charged.
This holds however the repeat happens:
Two of your reps scan the same visitor at the same booth.
The same person visits you at a different show later in the year.
The same person comes back to your booth at next year's event.
There is no time window on this and no annual reset. The first capture is charged, and repeats are not.
Scans that find nothing are also not charged
If enrichment cannot return verified contact data, no credit is consumed for that scan either.