TPG reader Ruth sent me a question on Facebook about maximizing points with online shopping:“Hi Points Guy, I have a question about double dipping in the AAdvantage shopping portal. If I go to gift certificates.com and buy a $100 cert at a store that is also on the portal, can one then turn around and use that certificate at said store via the portal?“Shopping through online portals is one of the best ways to rack up bonus miles and points on every dollar that you spend. Most airlines, hotels and credit cards have these online portals, which allow you to simply log in and then click through to a retailer for your shopping. In addition to earning the points you normally would by simply spending on your credit card, you also earn a separate bonus of whatever kinds of miles/points the portal offers that you can usually see deposited into your account within a week or two. So that’s a great way to double dip.Click through shopping portals like American’s for extra points and miles.What Ruth is asking is: can you go through a shopping portal once and buy gift certificates or cards and earn the bonus miles on that purchase? Then when you get those cards/certificates, can you then click through the shopping portal again and make your purchase with the gift certificates and earn another bonus?Technically, no. Most retailers and portals say that you won’t get any bonus points on gift certificate purchases. However, these portals don’t always have the best technology in place so it’s anyone’s guess as to how well they can track what kind of card or certificate you use to make a purchase after you’ve already clicked through to the merchant, so there are lots of reports (and I personally have had this happen) where people have done exactly what Ruth is talking about and earned bonus miles on both transactions.If you’re interested in testing this out, I’d recommend doing a little trial-and-error experiment to see whether you get the points or not on some small purchases before you commit to spending thousands of dollars on gift certificates you may not want to use - in case you don’t end up earning the bonus points you expect.Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.And if you happen to find any great deals - be sure to email me! I can’t promise I won’t share them with the rest of the TPG community, but in the end hopefully there will be a lot of bonus points for all of us.In the meantime, here’s a handy reference list of shopping portals:Air Canada: Aeroplan EStoreAmerican: AAdvantageEshopping.comAmtrak: Amtrak Guest RewardsBritish Airways: BA Miles EstoreChase: Ultimate Rewards ShoppingChoice Rewards: Choice Privileges MallDelta: Skymilesshopping.comDiscover: ShopDiscoverFrontier: Early Returns MallHawaiian Airlines: Hawaiian Airlines eMarketHilton HHonors: Hilton HHonors Shop to Earn MallMarriott Rewards: Shop My WaySouthwest: Rapid Rewards ShoppingUnited: MileagePlusshopping.comUS Airways: Dividend Miles Shopping MallVirgin Atlantic: ShopsAwayLet me know if you have any other questions by messaging me on Facebook, Tweeting me or emailing me at info@thepointsguy.com.[card card-name=‘Premier Rewards Gold Card from American Express’ card-id=‘22035076’ type=‘javascript’ bullet-id=‘1’]