The huge advantage of consolidating your old and new 401(k) accounts when you change jobs is that all of your money is in one place. You don't have to keep track of as much paperwork, and it's easier to balance the diversity of your portfolio if it's all right there on the same investment summary. You may also save money on fees if they are lower at your new 401(k) versus your older one. If you decide to move the money out of your old 401(k), you have two options: transfer it into a 401(k) at your new job or roll over the funds into an IRA.
Obviously, the first option is only possible if you already have a new job and your new company offers a 401(k) plan. The most important thing to understand when moving money from one 401(k) to another is the difference between a transfer and a rollover.
In a transfer, your old company sends a check directly to your new company and the money never passes through your hands. That excludes you from having to pay income tax on that money.
In a rollover, however, your old company makes the check out to you. Now it's your responsibility to deposit the full amount in your new 401(k) within 60 days or the money is taxed as income and you are slapped with an early withdrawal penalty if you're younger than 55. To make things more complicated, your old employer has to withhold 20 percent of your account balance, which will be returned to you as a tax refund. In the meantime, you need to come up with that 20 percent from your own savings in order to deposit the full account balance in your new 401(k). So remember: "Transfer good. Rollover bad."
If your new job doesn't offer a 401(k), or you don't have a new job yet, your other option is to roll over your old 401(k) funds into an IRA. In this case, "rollover" isn't a four-letter word. The money is sent directly to the IRA fund, and you aren't on the hook for any taxes. Most major investment firms offer rollover IRAs, although the fees vary, so shop around.