) -- Returning unwanted gifts is a holiday tradition, and the National Retail Federation estimates that consumers will return more than $46 billion in merchandise this season. But not all of that money is getting back to customers at the same time.

When you return a gift at a bricks-and-mortar store, you typically get your money back more or less immediately, either in the form of cash, credit or a gift card. But returning merchandise online is a bit trickier. StellaService, a firm that analyzes customer service practices for online retailers,

tested how long it took

to get a refund after returning a product to each of the 25 largest online retailers by standard USPS ground shipping.

As Americans send back their unwanted gifts, some online retailers will refund your money faster than others.

The big winner was

(AMZN) - Get Report

, which usually hits close to the top in any ranking that deals with customer service. (Indeed, the retailer just took the top spot in an annual

customer satisfaction survey

.) StellaService researchers found that it took just 4.3 days after the product was sent back to Amazon for their refund to show up back in their account. It's also worth noting that Amazon will generally give an instant refund upon printing out a return shipping label, with the understanding that the refund will be withdrawn if the merchandise isn't received within the allotted amount of time.

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The worst retailer in the survey was, the Web site for


beauty products. According to the researchers, they have yet to get their refund from the retailer as of Dec. 26. While it's not clear how long it's been since the Avon package was returned (the study was conducted in the "last few weeks"), we know that it's been at least two weeks, since the second-worst retailer,


(DELL) - Get Report

, took 14.3 days to issue the refund. Also interesting: Amazon shoe retailer

finished third-from-last in the rankings, taking 13.3 days to get the researchers' their money back. The company is noted for its 365-day return window, as well as its policy of

paying for return shipping

, but apparently that generosity comes at a price.

Here are the top 10 fastest refunders, along with how many days it took to process the refund.

1. 4.3 days


(BBY) - Get Report

: 4.7 days

3. 4.7 days

4. 4.7 days

5. 4.7 days

6. 5.0 days

7. 5.3 days


(WMT) - Get Report

: 6.0 days

9. 6.7 days

10. 6.7 days

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