You're missing the point.  There. Is. No. Equipment.

I understand what PCI compliance is, what it is for, and am probably one of the few that can actually answer all the technical questions.  But, when a client is ONLY using the functionality of emailing invoices through QBO that has a payment link that QB (Intuit) processes, the client has no access whatsoever to the credit card numbers. Never sees them.  Never stores the data.  Zero contact.  

THAT PCI compliance requirement is on Intuit.