Hi, I would like to ask if there is a way to customize the payment receipt (NOT the sales receipt) that I can send to the customer after I receive the payment.

Customizing payment receipts allows you to add or change details to better suit your business needs, pragma. However, the option is unavailable. 

I can see that this functionality is beneficial for you and your business. For now, I suggest reaching out to our product engineers with your feedback. They can take your suggestion into account for future updates. 

Here's how:

   1. Select the Gear icon, then choose Feedback.

   2. Type in your product suggestions.
   3. Select Next to submit.
 

As an alternative,  you want to explore third-party applications that offer the functionality to help you achieve your desired outcome.  Here's how:
 

   1. Go to Apps.
   2. Click Finds Apps.
   3. Browse for an receipt app in the Search for an app field.
   4. Click Get App Now if you found one.

In addition,  here' s an article to fine more details in personalising the sales form:  Customise invoices, estimates, and sales receipts in QuickBooks Online

Moreover,  take a look at the articles below for tips on how to send reminders for invoices and when they are due, as well running reports to know the company's well-being.

• Send invoice reminders automatically or manually in QuickBooks Online
• Run reports in QuickBooks Online.

That should do it! If you have other questions about managing customer payments in QBO, kindly add them below. I'll be sure to assist.