Their script goes roughly like this (I know this from numerous scambaiting calls; although there are different groups with slightly differing approaches, the original idea is the same everywhere):
When you call back they will first ask you for your telephone number. Why not your SSS or TIN? Their robocalls are systematic and based on lists with a small file attached to each number using information freely available over the internet (or sometimes compiled by less than honest call center workers). They will look up your file based on your number.
After they read their phony "affidavit" to you (can take several minutes) and threaten you with arrest within the next 45-60 minutes for tax fraud they will offer you a way out (because you have never been arrested etc.) by paying the IRS a fee that you have to transfer immediately (!) by "government certified bonds" (sometimes they use other lame explanations). These "bonds" turn out to be prepaid debit cards (like green dot money pak) and they will accept no other payment. They will ask you to take all the cash in your house plus whatever you can get out of an ATM, take it to the next CVS, Walgreens etc. that carries these cards (they will helpfully guide you to the nearest one using your address and - likely - google maps) and upload it onto the card. Then they ask you to read the codes from the back of the cards and while you are doing this they transfer it to different prepaid cards they have organized (or a paypal account) and the money is gone. Literally gone, you can't get it back and that's what they are after. All the while they make you stay on the phone so you can't call someone else or check the internet (which is an obvious risk to them as they might lose their grip on you), sometimes threatening you with jail time or other absurd things to keep you on the line. Senior citizens and immigrants are most vulnerable to this technique. Please spread this information as widely as possible to help protect others.