I don't know if anyone responded to this and I know I'm late responding, but thought it worth responding.
The closing date in QBO works exactly the same ad QB Desktop. You can set it as often as you want. If you are an accountant user, you can easily access from the Accountant Toolbox (briefcase in top toolbar) or from the Gear Icon/Account and Settings/Advanced.
When you set the closing date, it triggers the Exceptions to Closing Date report.
Hope that helps.
MB
MB Raimondi, CPA.CITPAdvanced Certified QuickBooks ProAdvisor
Certified: QB Enterprise; QB Point of Sale, QB Online
QuickBooks Solution Provider
ProAdvisor of the Year, 2019