A family member of mine that does not live with me anymore owes the IRS a considerable amount of money.
Here are several questions I have if the IRS comes to my door looking for them.
Should I tell them “No one lives here by that name”
Should I refuse to give them my name if they ask for it?
Can I tell them to leave?
Anything else I should or should not do or say?
As an honest man and a taxpayer yourself, if your relative stiffed the Feds, I would hope you would cooperate with the IRS in trying to track the relative down.
Why would you want to refuse to give them your name if you had nothing to do with the delinquency?
Of course, I empathize with your fear of the Federales given how the FBI has behaved recently.
As I understand the law [after watching L&O for 20 years] you do not have to offer anything, but if asked, you CANNOT lie.
Send them my way; Me and a lead pipe need to talk with them about the refund they owe me.
I don’t think law enforcement will come for them… they’ll just garnish their wages / Social Security until they tap out !
Things have to be very serious before the IRS shows up at your door. The standard method of communication is via letter. If the letter is addressed to you, you DO need to respond.
As for your liability, it depends not on where someone lives, but the nature of the relationship.
Why would you want to refuse to give them your name if you had nothing to do with the delinquency?
Because I don’t want them to harass me and start sending the letters to me because they can’t locate him
They will send letters to the person owing the taxes. If s/he used your address and a letter arrives, don’t open it. Just return it after writing something like ‘no such person at this address’ on the face of the envelope.
As has been said, return mail after marking it “not at this address” or similar. If you have a forwarding address, PROVIDE IT. That is the ethical thing to do. If you are not liable for the taxes, providing your name is irrevalent. But not providing it make it looks like you might well be liable. And by not providing information you know about this family member’s current location might be actionable… Why would you want to protect them if they left you out to dry?
Look at this way:
If you lived in a small town with one store where you bought groceries, hardware, medicine and all the essentials of life, and your family member ducked out of paying his bill there, and you knew his actions would result in you and everyone in town paying higher prices for everything… what would you do?
right, remember it is legal for the Federales to lie, even to trap you, but not for you to lie, or make a mistake if they decide to call it lying. 
Have you been caught in a sting operation? Would you rather our law enforcement agencies not use them?