If you are a CSRS employee, the Thrift Savings Plan (TSP) can provide you with a

source of retirement income in addition to your CSRS annuity. 

As a CSRS employee, you may elect to contribute any dollar amount or

percentage (1 to 100) of your basic pay to the TSP.  However, your annual

dollar total cannot exceed the Internal Revenue Code limit which is $15,500 for

2007.  

Although you do not receive any agency contributions, you do have the benefit

of deferring taxes on your contributions and on the earnings in your TSP account