The investment limit on tax-favored retirement savings plans such as the TSP will increase from $18,000 to $18,500 in 2018, the IRS has announced. That’s the cap on regular investments by employees, called the “elective deferral limit.” The separate limit on “catch-up contributions”–additional investments allowed for those 50 or older, or who will turn 50 during the calendar year–will remain $6,000.