My experience is with distribution but we use parent/child customer accounts regularly.
Within the customer record for each child account, go tothe Billing tab. There you can enter the customer ID for the parent account. Then when a payment comes in you can enter that as a payment from the parent and “Load Documents” which will bring in all existing invoices from children of that parent.
The other option is to enter multiple locations under one customer ID. You set those up under the Locations tab in the customer record.
We use the financial modules in Acumatica. We have a parent/child hierarchy to view customer connection of bill-to addresses and to evaluate overall performance and exposure. As mentioned above, under the Billings tab there is a section for ‘parent info’ and a field to enter the parent account ID. The parent account is a separate customer record. When viewing the parent account record, an additional tab will appear name “Child Accounts” and the linkage can be viewed there.