What does MBR mean when EIN is issued?

Answer 1

I our company's case I understood it to mean "member". I was the contact person for our Limited Loss Company, and MBR was inserted after my name in the official EIN document.

Furthermore, an IRS document found in the internet has this:

"A single member or sole member LLC account will contain the words "SOLE MBR" or "SINGLE MBR" within the Sort Name line as shown on CC INOLES"

So: MBR = member.