If I get covered by a new healthcare plan in the middle of a month that is already covered by COBRA, will I get double coverage or a prorated refund?

You have to ask two organizations:

• The new company. They will know when coverage starts. For most large companies it will be one day one. For many small companies it can be the first day of the next month, depending how their arrangement with the insurance company or benefits provider. The company I work for recently got large enough to be able to cover new employees on day one.

• The old company. They will let you know how to terminate coverage. Some could end it on a specific day, others will lock you in for the entire month.

Do I have the option of choosing between having a doubled healthcare coverage or getting a prorated refund for that time period (between February 15 and February 28) or is one of these two scenarios forced upon me by law?

I wasn't able to find any reference dictating that it must end on a specific day, only examples how some former companies have required full month, and others partial month.

Assuming that they will overlap, then it can be possible to get slightly better coverage. It is possible that one policy could pay for a medical expense, but the other would be considered secondary and help pay for some of your out-of-pocket costs. I have never done this but I have heard of others who have.

The big unknown is the cost of the double coverage, and what is the risk that you don't have coverage on day one. I would wait until after my first day of work, when I know everything about the new company, and then contact the old company and see what can be done. I would be contacting them anyway to make sure they don't accidentally charge me for March.