was it a fake coupon? how much was the coupon trying to save the customer? 50 cents off chips or something $$$. It could be considered fraud. If you are counterfeiting 1$ dollar bills it is still illegal.
no, it was not fake. But the real question is, is it a reasonable action to call the police for something like this? IN your chain of thought and chain of actions, why should the default be to call 9-1-1 for a fake coupon?
Your decision tree should not immediately involve the police for something like this.
As manager it should be something like:
#1) Ask customer where, how, why she got the coupon
#2) Look at your in store listing of coupons
#3) Look at the coupon and compare to in store listing
#4) Call supervisor / corporate and ask about the coupon
#5) Call originator / company of the coupon
#6) Ask customer if you can see the source that issued her the coupon (facebook, email, website, etc)
#7) Ask supervisor for permission to honor the coupon
#7a) If yes, honor the coupon
#7b) If no, explain why to customer and tell customer to have the originator of the coupon to contact store manager or owner
that is more or less the decision tree that should have happened here. It is very possible and likely that the customer may have gotten a fake coupon by accident from 1 of the bazillion websites out there that issue stuff all the time. It is possible that corporate is so big that they issue so many coupons that they lose track. It is possible she is confusing this coupon with another store's coupon...
But what is likely improbable is that she is creating a fake coupon. I mean, sure, it is possible but not likely as compared to all the other legitimate means of obtaining a coupon.
No where in the above should the police be involved. It's just stupid on so many levels. I mean, if you want to grasp for straws and find "some" mythical reason and justification for how she could be a criminal mastermind orchaestrating a fraud against the company then I guess you can go down that rabbit hole of improbability...
but seriously, calling the police for this is pretty stupid