Let me show you how to make changes to your financial reporting year in QuickBooks Online.
You can find the option to edit the start of the fiscal year and the closing date by going to the Account and Settings section.
Here's how:
Log into your QuickBooks account.
Click the Gear icon in the upper-right corner.
Below Your Company, select Account and settings.
Go to the Advanced tab.
Change the first month of fiscal year.
Enable the Close the books option.
Add a closing date if necessary.
Make changes to other information.
Hit Save, then press Done.
Additionally, I recommend the following resource which has video tutorials to help a user learn about customizing the settings, as well as some instructions about closing books: