Question: If a person is in the process of addressing a health problem at the end of the year and his insurance changes in January which is responsible for the health coverage?

Answer: It sounds like your employer-sponsored health insurance coverage has changed insurance carriers. It you have ongoing treatments that continue from 2011 into 2012, the old insurance is responsible for all medical services received in 2011 even though you may not be billed until 2012. Conversely, the new insurance plan will be responsible for all medical services with dates of service in 2012.