I think these are not for tax return audits, but rather new currency issuance. If the US were to switch from the dollar to any other form of currency either digital or physical all existing dollars would need to be swapped out before a certain deadline. Any dollars not changed by the appointed time would be lost forever. Bank accounts, 401k and all other securities would flip automatically but CASH will need to be deposited for the change to take place. All those hidden dollars, drug money, and other criminal enterprises, as well as savings under the mattress would be exposed to audit. That is where 87,000 agents come in.