In investing, the combination of safety and good returns is hard to find. One option that has held up well, though, is the voluntary contributions program, a little-known and even less-used retirement savings vehicle.

The program is only available to CSRS or CSRS-Offset employees, not FERS employees. It offers the opportunity to put up to 10 percent of career federal earnings in an individual account that is available to be withdrawn as a lump-sum at any time—either at retirement or before—or drawn out as an annuity after retirement.

The VC program is separate from the Thrift Savings Plan. Participation in one does not affect participation in the other. While the TSP is operated by its own agency, the Office of Personnel Management administers VC accounts. However, VC is often compared with the Thrift Savings Plan’s government securities (G) fund in that the returns of the two are generally comparable—and generally well above what is available through other guaranteed investments with similar liquidity, such as certificates of deposit or money market funds.

VC money is invested in government securities that in 2012 pay 2.25 percent. That’s a fairly low rate historically speaking for the program but it reflects the interest rates prevailing in the economy as a whole.

Like investments in the TSP, VC investments grow tax-free until withdrawn. But unlike the TSP, which allows investments to be made with pre-tax money, VC investments must be made with after-tax money. However, unlike the TSP, which generally requires investments only through biweekly payroll withholding, VC investments can be made at any time and in any amount, up to the lifetime ceiling. Thus, the VC program can be a good vehicle to hold proceeds of an inheritance, an investment gain or other lump-sum of money.

The form to open a VC account is SF-2804, available at www.opm.gov/forms.