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Depending on the referral offer, it's not uncommon for the person signing up to get a slightly lower bonus than those that may be otherwise publicly available or targeted to them at any time. However, the opposite can also be true (particularly with other lenders such as Amex), where a referral may be substantially better for the person applying. As for combining, no. The app must be done through the referral link, and whatever that offer is, is the one they get.