they say they are from the irs and threaten you by telling you that you owe money and you must pay or you will be arrested, loose your license and seize your assets.
Called my daughter and told her the IRS was filing a lawsuit and that she would be arrested if she did not transfer funds to cover back taxes (which she does not owe). Gave her one hour to contact them. I called the number and the answer and identify themselves as IRS. I called again and the identified themselves as a collection agency. When I identified myself as law enforcement they hung up.