A 401(k) plan is an employer-sponsored retirement savings plan that allows an employee to contribute a portion of his or her paycheck into a tax-advantaged investment account. The employee (or plan participant) typically chooses from a range of investment options within the 401(k) plan. These options, which often include mutual funds, are chosen by the plan sponsor—usually the employer. Approximately half of all assets in 401(k) plans are invested in mutual funds, which in turn are invested in stocks, bonds, and short-term investments.