If the clients says they received less than the $1400/person for EIP or $1500/$1800 per Child, they need to provide me proof before I do ANYTHING. 

Ideally, the actual IRS notices are best, but I will type up directions for how to get an Account Transcript at IRS.gov, and if they have trouble with that, how to fill out a 4506-T (with an explanation that may take a long time to receive that information).  They need to be responsible for getting me that information, so I won't do anything until I get that.