Amazon Prime customers may feel frustrated that they pay the $79/year fee only to find that their packages are still subject to the same delays as everyone else. But Prime members who carefully monitor their purchases can score free extensions on the service if a package is not delivered on time. And even if you’re not a Prime member, you can still get a discount if a guaranteed delivery date is not met.

The folks at DealNews.com tested Amazon’s policy of giving 1-month free extensions to Prime accounts for shipments that don’t meet their guaranteed delivery dates.

(NOTE: This extension policy does not cover free Prime accounts like Amazon Student and Amazon Mom, only paid Prime memberships.)

So when they realized their order of a roll of Spider-Man duct tape (which is apparently a thing that exists and you can buy) was a few hours past the guaranteed delivery time, they wrote to Amazon customer service and asked about whether they would be eligible for the free Prime extension.

Amazon wrote back, gladly extending the Prime membership for another month. This, in theory, could be done up to 12 times for a Prime shopper, so customers who do a lot of buying on the site — and who keep track of exactly when items are guaranteed to be delivered — can get two years of the service for the price of one.

Even those Prime customers who are in the 30-day trial period can score one free month of service by complaining about a late delivery.

DealNews says that non-Prime customers can have their shipping costs refunded if a guaranteed delivery date is not met.

Obviously, you should not file a false complaint or try to trick Amazon into giving you a free month of Prime. But when you’re annoyed that the UPS/FedEx/USPS driver hasn’t dropped off your Wolverine footie pajamas, it’s good to know that you have this option.

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