Having recently had a bad experience with them, they have posted an expanded explanation of their return policy on their website:
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Please note that we will issue a credit to your account within 24-72 business hours of receiving your returned merchandise. We have no control over how long it takes your individual bank to process refunds. Please contact your credit card or debit card issuer to find out specific details about how refunds are processed. From our experience, it can take up to 30 business days for credits to post to your account.
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They are right, they issue a credit within 24-72 business hours of receiving the returned merchandise. However, they use a separate company that takes care of debit card refunds, and I waited over 30 days for that credit to show up in my bank account because that separate company has a software problem with Mastercard debit cards. Knifecenter trys to blame it on the individual bank according to their return policy statement, but it is the company they use for credits that is the problem. So if you have a Mastercard debit card and you have to return some merchandise, be aware of this problem. You may be waiting a long time for a refund credit.