QuickBooks Online Sync Error: | A business validation error has occurred while processing your request | Business Validation Error: Select a customer for each billable split line.

Steps to Resolve the Billable Line Error in QuickBooks Online (QBO):

1. Check Your Company Settings: Go to Settings → Account and Settings → Expenses → Bills and expenses. Look for the "Make expenses and items billable" option. If it’s turned on and you don’t use billable workflows, turn it off and try syncing again.
2. Review Expense Accounts: Go to Settings → Chart of Accounts. Edit the expense account used on the bill. If it’s linked to billable tracking or defaults to "Billable," disable that option or use a non-billable account.
3. Review Products and Services: Go to Sales → Products and Services. Edit each item used on the bill and make sure it’s not marked as billable by default.
4. If You Must Keep Billable Enabled: On each bill in QBO, add a Customer/Project to any billable line item, or mark those lines as non-billable. Save your changes and then retry the sync.