The investment limit on tax-favored retirement savings plans such as the TSP will rise to $18,000 from $17,500. 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 in a calendar year—will rise to $6,000 from $5,500. Those who were making catch-up type investments in 2014 will have to make a new election in 2015; unlike regular investments, those don’t carry over from year to year.