What are the criteria for an exemption to paying penalties for an early 401k withdraw if you are 55?

[raynors]

I switched companies and rolled over the majority of my 401k but withdrew some.

[Opus 17]

If you are age 55 or older in the year you separate from the company, you can withdraw 401(k) funds without the 10% early withdrawal penalty.  However, you still owe regular income tax on any withdrawal from a pre-tax 401(k). 

[dmertz]

Just to make it clear, the exception only applies to a distribution from the 401(k) provided by the employer from which you separated from service in or after the year you reached age 55, not from any 401(k) of an employer from which you separated from service prior to the year you reached age 55.