Hank, 

Don and Angela both provided the definition and both of them are correct. However, there are many reasons why an individual transaction can downgrade, which increases costs of interchange from Visa. Late batch settlements or missing/ incorrect Address Verification Service (AVS) are a couple examples, however there are many different reasons. Run a quick google search to find a full list. Depending on which transactions and why those transactions are downgrading will determine who you would need to contact to address excessive EIRF downgrades. For example, you may need to contact your processor, however you may also need to contact your POS provider as well. 

Below are a couple resource sites to check out. 

https://www.cardfellow.com/blog/eirf/

https://www.cardfellow.com/blog/credit-card-processing-downgrades/