When it comes to dealing with 401(k)s from old employers, you need to think about fees and convenience.
You have a number of options when it comes to dealing with old retirement plans: you can keep your money where it is, you can roll over the old 401(k) into an IRA, or you can put all the money into your new plan if your new plan permits it.
The one thing you don’t want to do is convert it straight to cash. That will cost you taxes and a 10% fee if you’re under 59 1/2.
The biggest consideration is fees, the leech of investment returns. You want to pay the lowest fees possible. 401(k) plans at big companies often have very low costs, so if you left a Fortune 500 firm, you’re probably best to leave it alone. A good rule of thumb is that if your 401(k) levies expenses of more than 0.8% annually for a stock fund, look somewhere else.
You also want to be able to keep track of your accounts. If keeping tabs on three plans is too much for you, move the highest-cost one into an IRA or your current 401(k).