For some time now, the nation’s three major package carriers—DHL, FedEx, and UPS—have been offering next-day and second-day air delivery services for guaranteed delivery by specified times, such as by 8 a.m. or by noon. And customers have been paying premium prices for these earlier than normal deliveries.

Because not all of these deliveries get through to the consignee within the time specified, package carriers have established what they call Guaranteed Service Refunds (GSRs), providing refunds for late deliveries.

How many of these shipments are delivered late? While we don’t know of any specific research conducted on this, one company that audits carrier records for late deliveries told me that no less than 3 percent of guaranteed shipments are delivered late—and this number has run as high as 15 percent for some of that auditor’s clients. Millions of dollars of potential refunds are involved.

Since many companies don’t have the in-house expertise to perform such audits, many shippers have recently turned to auditors that specialize in uncovering late deliveries and filing claims for refunds. These auditors operate on a contingency basis.

Because millions of dollars worth of refunds are involved, over the last few years carriers have begun to place onerous restrictions on shippers who try to recover their refunds. Here are two notable restrictions imposed by individual package carriers.

1 Customers, or their auditors, are required to notify the carrier of a delivery failure no later than 15 days from the date the package in question was shipped. This is a particularly difficult requirement with which most shippers are ill-equipped to comply. Fortunately, auditors are set up to act within this short period of time.

2 Carriers have inserted into service agreements—which many shippers overlook and are not told about by their carrier representative—a provision that waives the shipper’s right to have the carrier process any GSRs.

One carrier, we learned, is offering its larger customers added discounts—usually 1 or 2 percent—if they agree to dispense with all refund filings. But how many small customers are offered such pricing concessions, or even know that such concessions are being given to the big guys?

One auditor we recently spoke with said a client was approached by its package carrier and was told that the carrier wouldn’t renew their service agreement unless they stopped using that auditor.

It’s very important that shippers remain aware of what lengths some package carriers are going to limit their exposure to GSRs. Don’t knowingly waive your company’s right to recover refunds that are legally due to your company. Carefully study every service agreement before signing it. And, if you see a provision you don’t like, let your carrier know you strongly object to it.

Stand your ground. After all, a guarantee is a guarantee.