Volcker Rule Relief Act of 2018 This bill amends the Bank Holding Company Act of 1956 to exempt from the "Volcker Rule" banks with: (1) total assets valued at less than $10 billion, and (2) trading assets and liabilities comprising not more than 5% of total assets. (The Volcker Rule prohibits banking agencies from engaging in proprietary trading or entering into certain relationships with hedge funds and private-equity funds.)