When a coupon is scanned, the store gives up money it expects to recover from the manufacturer. Getting it back involves a settlement industry most shoppers never see.
The store is fronting the discount
A manufacturer coupon reduces the price at the register, but the retailer has already paid wholesale cost for the item and receives nothing extra at the point of sale.
The retailer therefore submits the coupon for reimbursement of its face value plus a handling fee, printed on the coupon itself, that compensates for processing.
That handling fee is small per coupon and meaningful in aggregate, which is why large chains treat coupon processing as a managed operation rather than an afterthought.
Clearinghouses sit in the middle
Retailers send coupons to a clearinghouse that counts, sorts by manufacturer and forwards them for payment, then remits proceeds back to the retailer.
Manufacturers use redemption agents on their side to validate submissions against expected patterns before authorizing payment.
The process takes weeks, and disputes over counts and validity are settled between those intermediaries rather than at the store level.
Validation looks for patterns, not individual coupons
Redemption agents compare submitted volumes against distribution data for the region, since a store cannot legitimately redeem far more coupons than circulated near it.
Unusual patterns trigger investigation, and payment can be withheld while the submission is examined, which is where misredemption cases originate.
Coupon fraud is prosecuted federally in serious cases, because counterfeiting and mass misredemption cross state lines and involve mail and wire systems.
Digital coupons bypass the chain
A coupon loaded to a loyalty account is applied electronically, and reimbursement flows as data between the retailer and the manufacturer's promotion platform.
That removes physical handling, shortens settlement and gives the manufacturer redemption data tied to an account rather than to a paper stack.
It also removes the handling fee's original justification, which is one reason digital offers and paper offers carry different economics for the retailer.
The mechanics explain store policy
Restrictions on expired coupons, photocopies and coupons for products not stocked exist because the store will not be reimbursed for them.
Limits on the number of like coupons per transaction protect against redemption patterns that trigger a withheld payment on the whole submission.
A cashier refusing a coupon is therefore usually applying a rule about reimbursement rather than making a judgment about the shopper.