The standard maximum investment allowed in the TSP and similar retirement savings plans will remain $18,000 in 2017, the IRS has announced. That figure is a combined maximum for investors making both traditional, pre-tax, and Roth, after-tax, investments. The maximum “catch-up contribution” investment also will remain the same, $6,000. That’s an additional amount, also combined for those making both types of investments, allowed for those who are age 50 or older during the calendar year. The figures are adjusted by inflation but only once the accumulated amount since the prior increase passes a certain threshold.