Why record it per item
An inspector, or your own quality manager, should be able to see for any reagent which registration it relies on. If the number lives in a supplier email or a paper file, it is found only when someone remembers to look.
Keep it alongside batch and expiry
Registrations, batches and expiry dates are three separate facts about the same item. Holding them together means a single item page answers the questions an inspector asks, and expiring registrations can be flagged like expiring stock.
Make gaps visible
The useful report is not the list of items that have a number, but the list that do not. A simple view of untagged items shows the work still to be done.
Common questions
No. Vitrio records and tracks the registration numbers you enter and reminds you about expiry; it does not verify them with the regulator.
The NAFDAC field is part of the Nigeria setup. Other countries use their own regulator and registration fields.