In short, tiers are different categories and like buckets. Most commonly, they are split into 3 buckets, each assigned different percentage.QualifiedMid QualifieldNon QualifiedSince there are over hundred interchange fees based on the card brand, card type and business MCC code,  each merchant service providers desides which interchange category goes into specific bucket.  It varies from company to company and there is no way for us to find out.For example:An agent walks in and offers you  1.69% + $0.10 besides  the usual fees. What that really means is, they will charge you 1.69% +$.10 only on “Qualified” transactions.