Government Risk and Taxpayer Exposure Reduction Act of 2018 or the GRATER Act of 2018 This bill requires federal departments and agencies that administer credit, guarantee, or insurance programs to develop and implement a strategy and plan to transfer, to the maximum extent possible, the credit, guarantee, and insurance risk of the programs to the private sector. The strategy and plan must also address the utilization and development of private risk capacity in program and award development and administration. Federal departments and agencies that administer and award grants or aid must, in setting the terms for a new award, seek to utilize or encourage the development of, to the maximum extent possible, insurance risk capacity in the private sector in the United States and in foreign economies that receive or host grants or aid. The risk that is transferred to the private sector under this bill must be transferred at market terms, through a variety of financial instruments, and in a sustained and transparent manner.