Here is the explanation of the most common grant under what you asked, given that your client has CARES grant and not an ARP:

https://home.treasury.gov/policy-issues/coronavirus/assistance-for-state-local-and-tribal-government...

And here's what the IRS tells you:

https://www.irs.gov/newsroom/cares-act-coronavirus-relief-fund-frequently-asked-questions

And here are links for some of the other grants:

https://home.treasury.gov/policy-issues/coronavirus/assistance-for-state-local-and-tribal-government...

For example, the timeliness of SBA grants or USDA grants are not CARES grants, but people get the confused.