The steps required to add a sub-customer in Quickbooks Online
Complete these steps within your Quickbooks account
Step 1: Click Customers & Leads
Step 2: Click new customer
Step 3: The customer display name should equal the Xcelerate File number
Step 4: Click the check mark next to 'It's a sub customer'
Step 5: Choose the parent customer that corresponds with the file
Step 6: Click Save