There are several ways on how you can update your billing...
There are several ways on how you can update your billing information, corebuilt.
The option to update the billing info in QuickBooks Online (QBO) app is unavailable. If you paid for your subscription iTunes on your iPhone or iPad, follow these steps from your device on how to update credit card:
Open your device’s Settings.
Choose iTunes & App Store.
Choose your Apple ID, then View Apple ID.
Enter your Apple ID password.
In Account Settings under Subscriptions, select Manage.
Select your QuickBooks Online subscription.
If not, you can access your QBO account through the web and update your payment information.
Click the Gear icon on the top menu.
Choose Account and Settings.
Click the Billing & Subscription menu.
Click Edit ✎ next to Payment Method.
Enter your full credit card information by typing in the complete card number, name on the card, expiration date, and security code.
Click Confirm card.
Click Save Changes.
For more details about billing information, you can check out these articles: