President Trump's Farm Bill Reforms Act of 2018 This bill modifies several Department of Agriculture (USDA) programs to reduce farm subsidies and revise eligibility requirements. The bill includes provisions that: reduce crop insurance premium subsidies; eliminate the separate payment limitation for peanuts; terminate the use of commodity certificates to pay off marketing assistance loans; eliminate crop insurance premium subsidies and payments under conservation and commodity programs for farms with annual adjusted gross incomes that exceed $500,000; prohibit more than one person in a farming operation from qualifying as a farm manager actively engaged in farming for the purposes of receiving payments under USDA commodity programs; and limit the average rate of return for private insurance companies participating in the Federal Crop Insurance Program to 12% of retained premiums.