How do I stop pay a check issued using Online bill pay?

Try this following steps

You can go into the vendor, find the payment/check made to the vendor and open it?

Once opened, go to the VERY bottom of the page and click More (next to where it says Print Check/Order Check/ Make Recurring)

Click Void

That will make it so you can issue another payment/ check to that same vendor, for that same amount.

Good morning, @vbd.

How are you doing today? I hope all is well. 

If the bill payment is in “scheduled” status, you can go to the bill payment page, and select Cancel.

If our team has already processed the bill payment, the check has already been printed and sent. In this case, you'll need to contact our Customer Service Team so one of our agents can assist you further. Here's how: 

• QuickBooks Online Bill Pay Support

We recommend you contact the vendor and let them know you voided the check. Once voided, you may schedule a new payment directly to the vendor using the Bill Pay service.

For more information about this process, check out Learn about QuickBooks Bill Pay for QuickBooks Online. 

Please don't hesitate to let me know if you have any additional questions or concerns. Have a great day!