TSP Catch-up Contributions

If you are age 50 or over or will become 50 this calendar year, you may be eligible to make additional contributions to TSP, called “catch-up contributions.”
In order to be eligible, you must be planning to contribute the maximum deferral amount for the year. The maximum deferral amount includes deferred traditional contributions and Roth contributions.
Catch-up contributions have their own annual maximum; and, when combined with traditional deferred, Roth and combat zone tax excluded contributions, they may not exceed the annual addition amount.
The contribution limits may change each year and may be found at: https://www.tsp.gov/planparticipation/eligibility/contributionLimits.shtml
Catch-up contributions may be made as traditional or Roth contributions. Only basic pay may be contributed to TSP catch-up. Pay that is exempt for service in a combat zone may be contributed to Roth TSP catch-up but not to traditional TSP catch-up. Catch-up contributions, like regular contributions, must be made through payroll deduction. 
The Federal Retirement Thrift Investment Board has a fact sheet on Catch-up contributions at:

How to elect catch-up contributions

To elect catch-up contributions, Army, Navy and Air Force active component members and Navy reserve component members on active duty for more than 30 days should submit the form TSP-U-1-C, Catch-up Contribution Election, to their finance office. Army and Air Force reserve component and Navy reserve component who are drilling or on active duty of 30 days or less may start their catch-up contribution on myPay, but must submit the form TSP-U-1-C to change or stop their catch-up election. Catch-up contribution elections will be effective no later than the first pay period after submission.
Catch-up elections are only valid through the end of the calendar year in which they are made; therefore, contributors must submit a new election each year. Catch-up elections may be started, changed or stopped any time of the year.
Catch-up contributions will be invested according to your most recent contribution allocation. See the following web link for more information on allocating your contribution: https://www.tsp.gov/planparticipation/contributions/contributionAllocations.shtml
Updated Feb. 7, 2014