QuickBooks Online is not able to make recurring statements like it does with transactions. You can create a memorized report to email to yourself on a scheduled date each month as a reminder to log in and create your statements:

Setting up Recurring Customer Statements

  1. Go to Reports and click All reports.
  2. Click Manage accounts receivable.
  3. Click A/R Aging Summary or A/R Aging Detail (depending on how much detail you want to review in each emailed report). The report you chose will open.
  4. Click Save customizations at the top of the report. 
  5. Give the memorized report a unique name and click OK.
  6. Go to Reports and click My Custom Reports.
  7. Click on the Aging report to highlight it.
  8. Click Edit just above the Email column. The Memorized Report Settings screen will open.
  9. Select Set the email schedule for this report.
  10. Click Edit Schedule, set the schedule as desired, and click OK.
  11. Enter your email address in the To: field of the email form and click Save.