How do I apply one single credit memo to two different invoices?

Good day, KristinaP.

I'll help you split the credit memo between two invoices. Here's how:

1. Open the first invoice and click Receive Payment.
2. Click Discounts and Credits in the upper-part of the Customer Payment window.
3. Proceed to the Credits tab.
4. Check the credit memo that you created, then enter the amount in the Amount To Use column.
5. Click Done. 

Once done, proceed to the other invoice and follow the same steps to apply the credit memo. 

You'll also want to run the Customer Balance Summary or Transaction List by Customer report afterwards. The first report will give you a quick view how much is the current customer's balance, while the second one shows all the transaction made for this client.

Just go to the Reports menu, scroll-down to Customers and Receivable, and then select or click the report. 

The Community is always here if you need more help with your customer transactions.