Anyone who buys things online is missing out on travel rewards by ignoring free shopping portals from brands like Chase, Amex, and Southwest Airlines

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• Online shopping portals let you earn airline miles, hotel points, and other rewards when you make a purchase or sign up for a participating service online.

• Not only do most of the major airlines have their own portals, but some hotel programs do as well. Credit card issuers like Chase and Barclays also have their own shopping portals, but you need a credit card to utilize them.
• While you don't have to pay with plastic to utilize online shopping portals, you can "double up" on rewards if you do.
 For example, use the Chase Sapphire Preferred Card to make a purchase through the Ultimate Rewards portal and earn extra points.
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It's not hard to see why travel rewards have been growing in popularity over the last decade. You can use airline miles to pay for first-class flights that cost thousands of dollars, and you can use hotel points or credit card rewards to book hotels and even vacation rentals, along with rental cars, daily excursions and activities, and more.

The quickest way to earn points and miles is to sign up for a rewards credit card to earn a sign-up bonus and get rewarded for your spending. But credit cards aren't for everyone, and even if you don't want to add any plastic to your wallet, you still have options for earning points and miles to book travel.

Everything you need to know about shopping portals

Anyone can sign up for a travel brand's loyalty program. You don't need a card like the Southwest Rapid Rewards Performance Business Credit Card to join the airline's Rapid Rewards program, for example, nor do you need the Marriott Bonvoy Brilliant™ American Express® Card to sign up for the Marriott Bonvoy program. In fact, you should sign up for the programs of any airlines and hotels you travel with, since you'll earn points or miles on your paid bookings.

Travel shopping portals offer yet another way to earn airline miles and other types of rewards, and some don't require you to have a credit card at all.

All the major airlines have shopping portals

If you're a frequent flyer who wants to earn airline miles without a credit card, you should check out the major airline shopping portals. Most of the big players have them - United Airlines, American Airlines, Delta Air Lines, and Southwest Airlines, to name a few.

With each of these portals, earning more miles is easy. All you have to do is sign in to your frequent flyer account, search for the store you want to shop at, then "click through" the portal to the store and make purchases as usual with any form of payment.

While participating stores change all the time, you can usually earn 2 bonus miles or more for each dollar you spend at stores like Macy's, Kohl's, and Staples.

Some hotels also have shopping portals

If you're a hotel loyalist who racks up miles in a specific hotel program, also remember that some hotels have their own shopping portals. For example, Choice Privileges' shopping portal lets you earn bonus points any time you click through and buy something from a participating retailer.

If you love earning hotel points and you're going to shop online anyway, why not take advantage?

You can also earn points on services like internet

Big purchases like a mattress or furniture are an especially good way to boost your points haul. But remember that some travel portals let you earn points or miles on more than just "stuff" you buy. With Southwest Rapid Rewards, for example, you can frequently rack up points for setting up new phone service with Verizon (currently 3,600 points) or setting up AT&T internet (currently 3,600 points as well).

You can 'double up' on rewards with the right credit card

Finally, don't forget that you absolutely can use a travel rewards credit card when you shop through travel portals. In fact, doing so can be very beneficial since the rewards you earn in a portal are doled out on top of the rewards you earn with your credit card.

Let's say you plan to shop at Kohl's through the Southwest Rapid Rewards Shopping portal. Currently, you would earn an additional 2 points for each dollar spent through the portal, but you could earn another 1 point for each dollar spent by paying with your Southwest Rapid Rewards Performance Business Credit Card.

Just remember that, like with any other purchase, you do have to pay your credit card balance in full each month to avoid credit card interest and its evil cousin, debt. If you rack up balances and carry them month to month, the extra rewards you're earning through a portal won't be worth it.

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Please note: While the offers mentioned above are accurate at the time of publication, they're subject to change at any time and may have changed, or may no longer be available.