Hi we made a payment to a creditor. we did not have the invoice at the time and an expense was created. Can I change this now to a bill payment. Will it effect my bank?

Yes, you can, @silverton-leeann.

You'll want to open your expense transaction and change the category to Accounts Payable (A/P). This will make the amount of the expense an open credit and can be apply as a bill payment. And no, this will not affect your bank. I'll show you how.

1. Log in to your QuickBooks Online (QBO) account.
2. Open the expense transaction and go to the Account details section.
3. Change the affected account in the CATEGORY column to Accounts Payable (A/P), and click Save and close.
4. Open the bill, and click the Make payment button.
5. In the Outstanding Transactions section, mark the bill you want to pay.
6. From the Credits section, mark the expense transaction. We'll use it as payment.
7. Make sure the AMOUNT PAID is equal to zero (0.00). 
8. Click Save and close.

In case you need to refund your supplier in QBO, you can refer to this article for the step by step process: Handle supplier credits and refunds in QuickBooks Online.

Whenever you need help managing your suppliers and bills, you can always count on me to back you up. Stay safe and have a good one!