Hi Hank, EIRF (Electronic Interchange Reimbursement Fee) is a downgraded Visa transaction that commonly happens because of but not limited to:

• Not settling within 2 days of the authorization
• Forcing transactions (including voice authorization)
• Failure to respond to all Address Verification Service (AVS) prompts

Hope this is helpful and if you would like an assessment of your overall interchange fees I'd be happy to provide that to you.
Inez Deaton
xxx-xxx-xxxx