Hi salgado1,

It's a pleasure to see you in Community.  Welcome back!  Creating a credit memo in QuickBooks Online is a great way to reduce the customer balance on their next invoice.  However, when it come to sales tax, this can cause a negative impact on other areas of your books.  In this situation, I recommend reaching out to your accountant for their expertise and best course of action.  If you don't have an accountant, we can help you locate a ProAdvisor in your local area.

Should any other questions come to mind, feel free to reach back out.  We'd be happy to help!