A 401(k) plan set up for an individual running a sole proprietorship or a small business with a spouse/immediate family member. Plan contribution limits for the individual are equal to a typical company-sponsored 401(k), but the sole proprietor can also make an employer contribution to an independent 401(k), thereby raising the total contribution allowed.

The independent 401(k) may also be called a "solo 401(k)" or an "indie K".

Watch: Introduction in 401(k)

As with standard 401(k) plans, catch-up contributions are allowed for those above age 50 who have indie 401(k)s - up to $5,000 in 2006. Contributions made to the plan as an employer are also tax-deductible, which can help to save the sole proprietor a great deal in taxes.

The independent 401(k) offers many of the same features as a Keogh plan or an SEP IRA, but an independent 401(k) can be cheaper to establish and maintain, and loans are often allowed against an independent 401(k).

The major drawback to the independent 401(k) is that no outside employees can be hired, or the window of applicability closes.