Answer by John Burnett: If it's a government account, it could stand for "Alcohol, Tobacco and Firearms."
But it's most likely the abbreviation for "as trustee for."
Answer by Ken Golliher: I suggest that your bank should not open accounts using initials or terms that have no specific meaning to you or are not explicitly recognized by state law. Customers are more imaginative than bankers and they may fervently believe that the acronym or term means exactly what they think it does.
First published on BankersOnline.com 2/25/13