The billing simulation report is critical to your billing system. This report will simulate the actual billing run that happens at 12.01am PST on the 1st. Generate this report, note any incorrect invoicing, fix in your billing system and run this report again.
Please run this report until the billing is accurate.
Go to Business Tools > Invoices & Payments
Click Billing Simulation.
Open the Excel spreadsheet it generates.
Once billing is run, mistakes need to be manually fixed through credit or debit invoices. Billing cannot be rolled back to fix errors.