Hi @DJ_Pérez,
I got your back on this query about a client's subscription.
It's necessary for your client to have a QuickBooks Online (QBO) subscription, as well as invite you as an accountant user to their company. You can forward this article to them in case they need help on how to proceed: Invite an accountant to review your accounting in QuickBooks Online.
I suggest you view this article as well: Use accountant tools and features in QuickBooks Online Accountant. It's a complete list of features and tools available for our users with the QBO Accountant, along with their short descriptions. Related links are provided for your reference too.
Place a comment below if you have other concerns. I'll get back to you as soon as I can.