Rebates are payouts from Utilities, and maybe a State Energy program. The IRS gives Tax credits, as do some States for some equipment. Make sure to read about this from the perspective of Personal, not Commercial or Generating, property.

Did you try the Web:

https://clippercreek.com/evse-rebates-and-tax-credits-by-state/

https://www.chargepoint.com/incentives/federal-tax-credit-home-ev

For the vehicle credit, it varies by vehicle and year.

Keep in mind that most likely, your taxpayer has been very misled by the people in this industry, into believing a bunch of money might come from these purchases.