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You get options if you’re joining Costco. You could either pay $65 a year for a basic Gold Star membership, or upgrade to an Executive membership for $130 a year.

The benefit of the Executive membership is that it gives you 2% cash back on your purchases. Throughout the year, that extra cash could add up nicely.

Executive members get a rewards certificate each year that represents the cash back they’ve earned. You can then use that certificate to pay for a host of purchases at your local Costco store.

But there are limits as to how you can use your Executive membership rewards. Here are three things you unfortunately can’t spend it on.

1. Gasoline

Gas purchases at Costco are not eligible to earn 2% cash back on an Executive membership. Similarly, you can’t use your rewards certificate from that membership to pay for fuel for your car at Costco’s gas stations.

That’s not such a terrible thing, though. First, Costco happens to sell some of the cheapest gas in town, so having to pay out of pocket to fill your car may not be such a budget-buster.

Plus, if you use the right credit card at the pump, you can save plenty of money. Click here for a list of the best credit cards for gas rewards.

2. Food court meals

One of the perks of shopping at Costco is getting access to the store’s food court. Whether you’re a fan of the jumbo-sized pizza slices or the famous $1.50 hot dog and soda combo, a food court stop is a great way to top off a Costco shopping run.

However, you can’t use your Executive membership rewards to pay for food court purchases. But seeing as how the most expensive item at the Costco food court is a whole pizza for $9.95, that’s not awful.

3. Anything from Costco.com

Purchases you make on Costco.com are eligible for 2% back on an Executive membership. But surprisingly, you can’t use your rewards certificate to pay for online purchases. You have to redeem your rewards certificate in an actual store.

That said, there’s a workaround. If you want to use your rewards certificate for a Costco.com order, you can redeem it at a physical store to pay for a Shop Card, which is Costco’s version of a gift card. You can then use your Shop Card to pay for an online purchase.

Even though you can’t use your Executive membership reward for certain Costco purchases, it’s still worth upgrading your membership if you think you’ll spend more than $3,250 a year at Costco. It takes exactly $3,250 to break even on the $65 upgrade fee, and any money you earn beyond that point is free cash to enjoy.

However, if you decide that the Executive membership isn’t right for you, you can still score cash back on your Costco purchases by shopping with the right credit card. Click here for a list of credit cards that reward Costco members generously.

Top credit card to use at Costco (and everywhere else!)

We love versatile credit cards that offer huge rewards everywhere, including Costco! This card is a standout among America’s favorite credit cards because it offers perhaps the easiest $200 cash bonus you could ever earn and an unlimited 2% cash rewards on purchases, even when you shop at Costco.

Add on the competitive 0% interest period and it’s no wonder we awarded this card Best No Annual Fee Credit Card.

Click here to read our full review for free and apply before the $200 welcome bonus offer ends!

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Motley Fool Money does not cover all offers on the market. Editorial content from Motley Fool Money is separate from The Motley Fool editorial content and is created by a different analyst team.Maurie Backman has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Costco Wholesale. The Motley Fool has a disclosure policy.