I am categorizing numerous checks downloaded from bank account, but when I enter a payee name, and account number, it makes the same change to all uncategorized checks.

Let me help you find out why this is making the same change to all uncategorized checks, Scotty.

You'll want to make sure that the Enable suggested categorization option under the Transaction details section is untick so QuickBooks is unable to make some changes to your other transactions. To show you how, follow the steps provided below:

1. On the Banking page, click the Gear icon.
   
2. Uncheck the Enable suggested categorization box.
   

On the other hand, I see you haven't created a bank rule for your transactions. However, if it is still doing the same, there's a possibility that other users are setting up certain bank rule for some transactions. You can double-check them again. Here's how:
 

1. Go to the Gear icon, then select Rules. 
2. If there are rules, tick the box to disable or delete it. 
   

Furthermore, to know more on how you can review your accounts to ensure they matches your credit card and bank statement check out this article on how you can reconcile them. This will give you a step-by-step process on how you can reconcile your account: Reconcile An Account in QuickBooks Online.

Reply below if you need further assistance about categorizing transactions. We're always here to help you anytime. Have a nice day!