Thanks for posting in the Community! If you'll no longer be using your QuickBooks Online account, it's best to cancel the subscription to avoid getting billed for the monthly subscription. Just make sure to export all reports and lists needed to back up your data and for record keeping prior to cancelation.
Here's how to cancel your subscription:
Log in to QuickBooks Online as the master admin using a web browser.
Click on the Settings icon, and click on Account & Settings.
Click on Billing & Subscription.
In the QuickBooks section, click on Cancel subscription or Cancel online.
Follow the onscreen prompts.
Once done, your data will be available in read-only access for 1 year from the cancellation date.
To learn more about the cancelation of QuickBooks Online, check this link