It's a telemarketing scam for sure. Telemarketers posing as the IRS saying you owe money is an ongoing scam. Best bet is to not answer calls from numbers you're not familiar with and/or block them. In fact, get a call blocker. You can safely block certain entire area codes right off, like 100, 200, 300, 400, 500, 600, 700, 800, 888, 900. And after that start blocking area codes from parts of the country where you don't know anyone. I use software which works with TWC to block unwanted calls. I typically get 50 to 100 junk calls a week, but now only 1 or 2 ever get through (and those numbers are promptly added to the block list so they never get through again).