Whether you are self-employed or a W-2 employee, there is not a limit to the number of 401(k) plans you can have. Sometimes due to change of jobs you may have other plans left behind. However, you can only contribute to the plan where you are currently employed or an active participant. In addition to an employer sponsored 401(k), you can also have a Traditional IRA or Roth IRA even if you are making contributions to a 401(k).