Add each location as its own customer. Then decide two things: who gets the invoices, and who pays them.
A customer group's preferred billing address sets who gets the invoices. Its Billing Account sets who pays. To learn more about each, see choose who pays and who gets invoices.
Each location gets and pays its own invoices
This is decentralized billing, and it needs no setup. Leave the locations out of a group, or group them for reporting only, with no group billing address and no Billing Account. Each location gets its own invoices and pays with its own card or bank account.
Head office gets the invoices, each location pays
In Customers > Groups, put head office and its locations in one group.
On the group's Profile tab, click ⋯ on head office's address and choose Set as preferred billing.
Leave Billing Account empty.
Every location's invoices now go to head office. Each location still pays with its own saved payment method.
Note: Head office has to be in the group. The group's address list only shows its members' addresses.
Head office gets and pays for everything
This is centralized billing.
Set up the group as above, with head office's address as the preferred billing address.
Open the group, click Edit group (✎), and pick head office as the Billing Account.
In Settings > Collections > Account statements, turn on Enable automatic statement emails.
Under Statement Recipients, choose Customers not in a group, and customer groups, then click Save changes.
The group now gets one statement for every location, and the locations don't get their own. If head office is on QuickPay, its saved payment method pays overdue invoices for every location.
Tip: To send the group statement and a statement to each location too, choose All customers, and customer groups in step 4.
Who can use this feature?
Team members with Customers access
Team members with Settings access, to turn on statement emails
Available on all plans. A Billing Account and group statements need Scale or Enterprise.