Can I change an expense to a bill payment for a vendor?

Changing transaction type in QuickBooks is unavailable, FYGH. However, modifying the Category Account in your expense transactions to Accounts Payable (AP) account will allow you to link them to your bill payments.

I'll guide you how:

1. Go to the + New icon and then select Expense.
2. Select the name of the payee.
3. On the Category details section, select Accounts Payable.
4. Enter the other necessary details. 
5. Click on Save and close.

Then, here's how to add the expense to bill payment.

1. Go to the Expenses menu and then select Expenses.
2. Locate the transaction, then click to open.
3. On the right side of the screen, click Add.
4. After that, click on Save and close.

Here are some articles that'll help you in handling vendor balances in QuickBooks Online:

• Enter a Credit From a Vendor
• Resolve A/R or A/P Balances on a Cash Basis Balance Sheet

Additionally, I've added an article about creating a refund from a vendor. This helps you ensure that all the transactions are recorded accurately: Enter A Refund.

Please get in touch with us again if you need help in managing your transactions in QuickBooks. This way, we'll be able to further assist you.