If I "combine payments" to a vendor, will a memo be included with that payment detailing invoice numbers paid?

Hello there, Dawn. Let me share what will happen to your memo when you combine two payments.

Combining two payments from the same vendor will save you time paying bills and make it easier for us to apply for the credit. 

When we merge payments, its credit memo will not combined. However, we can manually add the credit memo after combining those payments.

Here's how: 

1. Go to + New, then click Credit memo.
2. In the Customer dropdown, select the customer's name.
3. Enter the credit memo details, such as the date and the amount.
4. When done, select Save and close.

After this, here are the steps to combine payments: 

1. Go to Expense, and click Vendors. 
2. Tick the checkbox with the correct vendor.
3. Select Make payment. 
4. On the Bill Payment page, check all Bills you want to apply for the credits.
5. Once done, Save and close.

If you need more help recording your client refunds, you can check this article: Record a customer refund in QuickBooks Online.

Don't hesitate to reply to this thread if you need additional assistance applying credit memo in QuickBooks Online. I'll keep an eye out for it. Take care.