Welcome to the QuickBooks Community, @Biocyclic.
In QuickBooks Online (QBO), closing your books will prevent doing changes in your past transactions. This is usually done when you reach the end of an accounting period to prepare to file your tax returns. For more info about this, please see this article: Close your books in QuickBooks Online.
Then, in starting your fiscal year, you'll need to set up the first month of your financial year. To guide you with the process, check out this link: QuickBooks Online year-end guide and checklist.
In case there are changes you need to do with your closed books, such as edit the closing date or you've forgotten your password, no worries because QBO will let you edit both.
If there is anything else you need to know about closing your books in QBO, please let me know in the comment section below. I'll be always here to lend a hand. Have a good one.
