Welcome to the Community, @HemLaw16.

Let me provide some ideas about customizing check stubs in QuickBooks Online (QBO).

The option to customize the check stubs is unavailable in QBO. The account number will be present to all check stub pages. 

Meanwhile, I recommend visiting our QuickBooks blog to stay current with the news and product updates. You can check out this site from time to time through this link: https://quickbooks.intuit.com/blog/.

You'll want to know how to print check stubs in QBO. Please browse this article for the steps on how: How to print check stubs.

I'm always around to lend a hand if you need more help with managing your check stubs or any QuickBooks-related concerns. Take care and stay healthy.

is this something QBO is working on?   it's an important piece of information needed on the check stub we keep with the invoice paid.

will this be updated soon?

Same issue for me.  When is QB Online going to correct this??

Hello there @hallandsons, thanks for being part of the QuickBooks Community!  

@ReyJohn_D was correct that we are unable to customize check stubs at this time, but we appreciate this valuable feedback and and I know our developers do too!

While I don't have any information to share on this feature right now, you can always submit your feedback and ideas to our development team to let them know it is important to you:

1. Select the Gear icon at the top, then Feedback.
2. Enter your comments or product suggestions then select Next.
3. Select Skip and send message.
4. From the drop-down, choose the appropriate category, then select Send message.

Your feedback goes to our Product Development team to help improve your experience in QBO. You can track feature requests through the QuickBooks Online Feature Requests website.

Please feel free to reply if you have additional questions, have a great day!

You mention that the account will be present on all check stubs.....but right now it does not print on any of the stubs (I am not using payroll....just  paying invoices).  In the desktop version, I could customize the check stub but evidently not in the  online version which I am now using.  How do I get the account to show on the check stubs?

Thanks for joining the thread, @dotsy. Let me share some information about the check stubs in QuickBooks Online (QBO).

Upon checking here on my end, there's no account number shown in the check stubs nor when printing it. However, if you really wish to add it when printing the checks, you can manually input it from the Memo field. I'll show you how:
 

1. Go to the Payroll menu, then Employees.
2. Select an employee, then click the Paycheck list.
3. Choose a specific pay date then select Edit from the Action column.
4. From the Memo field, enter the account number.

Moreover, unlike the QuickBooks Desktop, we're unable to customize check stubs in the Online version. I understand the importance of having the option to customize and show the account number on check stubs.

As a valued QuickBooks customer, we'd love to have your input about the enhancements you'd want to see in QBO. That being said, I recommend sending feedback to our product developers so they can review which parts of the program need enhancements and consider adding them to future updates.

You can do so by going to the Gear icon, then clicking Feedback. Check out this link if you want to track your feature requests: QuickBooks Online Feature Requests.

There are times when you encounter issues after printing your paychecks. To rectify this, follow the steps provided by this link: Troubleshoot printing paychecks, pay stubs, and forms in QuickBooks Online Payroll.

Should you need further assistance printing paychecks, don't hesitate to leave a reply. I'm always around to lend a helping hand. Take care.