Let me share some information regarding sending customer statements every 1st day of the month using QuickBooks Online (QBO). Currently, only the QBO Advanced plan has this feature. To use this, you'll need to upgrade your account to access this functionality. Let me show you how to.
Go to Workflows, then select Templates.
Find and click the Send recurring statement to customer.
On the Create workflow, add the necessary details.
Once done, click Save and enable.
Moreover, If you don't consider upgrading your plan, I suggest sending statements to your customer manually by doing the steps I'll mention below.
Go to Customers & leads, then select Customer.
Choose the customer for whom you want to make the statements.
Click the New Transaction dropdown, then select Statement.
Review everything, then click Save and send.
The Send Statement window will show, and the PDF preview will show, edit or add necessary details, and then hit Send.