Agency Conferences and Conventions Operating Under Necessary Transparency Act of 2012 or the ACCOUNT Act - Requires the head of a federal agency to: (1) approve in writing any conference costing more than $25,000, (2) approve such a conference only upon determining that it is necessary to the core mission of the agency, and (3) publish a summary on the agency website of the conference that includes the purpose and total cost of the conference and the cost per employee that attended the conference.