We can locate the cancel button on your company settings.
Go to the Gear icon, select Account and Settings.
From the Billing and subscription tab, click select Cancel.
Click Continue to cancel.
Though, you're account will no longer active, you can still access your company data for a year. After that, QuickBooks Online will permanently delete your company data. I suggest printing all reports and forms before cancelling your account.
Comment below if you need more help. I;ll always be here to assist you.