Can I attach or create a bill for a payment that was made in advance?

Allow me to share a few information about entering a bill that was already paid, Mary June.

Generally, if you plan to pay for expenses in the future, you'll have to enter it as a bill. On the other hand, if you've already paid for a business expense, you can enter it as an expense. To record expense transactions, you can follow the steps below: 

1. Select + New. Then select Expense.
2. In the Payee field, select the vendor. 
3. In the Payment account field, select the account you used to pay for the expense.
4. In the Payment date field, enter the date for the expense.
5. In the Payment method field, select how you paid for the expense.
6. If you want detailed tracking, enter a Ref no or Permit no. This is optional.
7. In the Tags field, enter the preferred label to categorize your money.
8. In the Category details section, enter the expense info. In the Category dropdown, select the expense account you use to track expense transactions. Then enter a description. Tip: You can also enter specific products and services in the Item details section to itemize the expense.
9. Enter the Amount and Tax.
10. If you plan to bill a customer for the expense, select the Billable checkbox and enter their name in the Customer field. Then, select Save and close.

While recording checks is the quickest way to record payments, this is used when no bills are received or to pay bills as soon as you receive them. Please check this article for more information: Learn the Difference Between Bills, Checks, and Expenses in QuickBooks Online.

For your reference, learn how to customize a report to make sure you'll get the information you need: Customize Reports In QuickBooks Online.

Keep me posted if you have any concerns about bills and payment. I'll always be right here to help.

@Mary June 

You can enter the check and assign it to 'Accounts Payable'.  This will create a vendor credit and reduce the checking account balance.  Then, when you receive the bill, enter the bill and apply the credit to pay it.