I'm here to help you fix the incorrect receive payment in QuickBooks Online, @heidi4.

We can delete and recreate the incorrect payment. After, apply this to the correct invoice. Let me show you how:

1. Go to the Sales menu.
2. Go to the Invoices tab and find the invoice with the incorrect payment.
3. Double click the transaction to open it and click Edit invoice.
   
   
4. Select the Payment made link and the date.
   
   
5. Select More in the footer. Then select Void or Delete.
6. Select Yes to confirm.

To record the payment to the correct invoice, follow the steps below:

1. Go to the + New button.
2. Choose Receive Payment.
3. From the Customer dropdown, select the name of the customer.
4. From the Payment method dropdown, choose the payment method.
5. From the Deposit to dropdown, select the account you put the payment into. 
6. In the Outstanding Transactions section, click the checkbox for the invoice your recording payment for.
7. When you're done, click Save and send to resend this to your customer.

For more insights, feel free to browse this article: Record invoice payments. It includes few ways how to record sales transactions in QuickBooks Online. After, you can resend and email your invoices.

I'm also adding this link to help you deposit payments in QuickBooks. 

Let me know in the comment section if you need help managing invoices in QuickBooks. I'll be more than happy to help. Have a nice day.