I have received deposit invoice payments. However the work was not done. These payments are now sitting as unapplied payments. I need to send the a credit memo.

Let me help you on creating a credit memo, suzannek1. 

In QuickBooks, when you create a credit memo, it credits your Accounts Receivable (A/R). That explains why when you created a credit memo, the amount of credit doubled. I can give you some steps that help you clear out the unapplied payments. 

Step 1: You need to create a bank account for you to deposit invoice payments that you received. Then save your account under Accounts Receivable(A/R). 

Step 2: Create a Service Product. Enter the name of the service product same as the deposit invoice payments. 

Step 3: Create a journal entry. 

• Debit the product that you've created.  
• Credit the newly created bank account. 

Step 4: Receive Payment and choose the customer that you want to create a credit memo with. As you choose that specific customer, you can see its journal entry and the unapplied payments.

Step 5: Create a credit memo. Then select the service item that you created earlier for the amount of the unapplied payments.  

You may use this article as a guide if you want to see your financial reports: Run reports in QuickBooks Online. 

Feel free to reply whenever you have further question/s about the credit memo. I'm always here to assist you.