It doesn't matter whether you left voluntarily or was laid off..if you pay the entire cost of the premiums plus a one or two percent administration fee you can continue your group health coverage for 18 months.
As I understand it the COBRA provision in the "stimulus" package applies to workers 55 and older. If they wish they can continue on COBRA for ten years, versus the usual 18 months, until they are eligible for Medicare. Of course that means ten YEARS of making that premium payment.
As for pre-existing...once you leave a job, voluntarily or not, you will receive what is called a HIPAA letter. It is a letter of creditible coverage that states you were once covered under group health insurance. What it does is protect you against any pre-existing provisions of a new employer sponsored plan or an individual policy. It is VERY important that if you do end up trying to secure an individual policy that you do it within 60 days of losing your employer sponsored health insurance.
http://www.dol.gov/ebsa/newsroom/fshipaa.htmlThe Health Insurance Portability and Accountability Act (HIPAA) offers protections for millions of American workers that improve portability and continuity of health insurance coverage.
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Certificates of creditable coverage must be provided automatically and free of charge by the plan or issuer when an individual loses coverage under the plan, becomes entitled to elect COBRA continuation coverage or exhausts COBRA continuation coverage. A certificate must also be provided free of charge upon request while you have health coverage or anytime within 24 months after your coverage ends