First Responder Fair Return for Employees on Their Initial Retirement Earned Act of 2021 or the First Responder Fair RETIRE Act This bill allows disabled federal first responders (e.g., law enforcement officers, customs and border protection officers, and firefighters) to continue receiving federal retirement benefits in the same manner as though they had not been disabled. Under current law, federal first responders are subject to a mandatory retirement age of 57. To facilitate this earlier retirement, federal first responders are required to pay a greater percentage of their salary towards retirement. Additionally, their annuity amount is calculated at a higher rate than other federal employees. This bill allows a federal first responder to remain in the accelerated retirement system if they are placed in another civil service position outside of that system after returning to work from a work-related injury or illness. Further, if such an employee is separated from service before they are entitled to receive an annuity, they may receive a refund of their accelerated contributions.