Most of what you read on financial planning in the media is garbage, but here is one of those occasionally useful pieces: IRA Rollovers Could Have Tax Implications.
Here’s the idea: You keep company stock in your qualified plan aside from any rollover you may do. Leave it with the company. Convert it to non-qualified money, which means you take the hit for ordinary income at whatever you paid for the stock, or its value at time of acquisition(consult a tax professional. There used to be some circumstances where you could substitute other assets of equal value, and avoid the ordinary income hit altogether). Hold them for one year or more after conversion.
Now, if you sell them, you’re talking about long term capital gains, rather than ordinary income tax, a much lower rate, and subject to your control as to when you realize it.
Because it’s no longer part of your IRA, you are not paying ordinary income tax rates on the whole amount as you take it out of the account. Nor is it subject to Required Minimum Distribution (RMD) rules that the IRS has. You pay only capital gains tax when and where you redeem them, as you redeem them. Capital gains is a much lower tax than ordinary income, provided you hold for at least one year.
This is not for every qualified account. Since Roth 401s are after tax accounts, the whole thing is rather self defeating if the assets should be held in one of those, or in a Roth IRA for that matter. Why would you want to do this to conserve taxes if there are no taxes due if you just do nothing?
Now, by and large, I recommend moving your money to an IRA of equivalent nature when you leave a company. Traditional 401k to Traditional IRA, Roth 401k to Roth IRA. But as you can see from this, there are exceptions to that general rule.
Caveat Emptor
(Postscript: My wife is the IRA clerk for a fairly large local institution. You would be amazed how often people get bad advice from generic tax farms, and how often theoretically competent professionals do the rollover forms wrong. This highlights the fact that just because they work for Famous Well Known Corporation, doesn’t mean they know what they’re talking about. Matter of fact, I’ve regularly seen people working for Famous Well Known Corporations give awful advice that cost clients money, and would lose the business permanently to anyone else. But people cut Famous Well Known Corporations way too much slack. It is a better strategy to consider the individuals who will be performing your services.)