I understand the importance of customizing the sales receipt, @Mmm16sf. Let me chime into this matter. 

As my colleague mentioned above, customizing receipt templates is currently unavailable in QuickBooks Online. However, you can send a feature request to our Product Developer team to add this to the future updates of the program. 

To send a request, you can follow the steps below as your reference:

1. Click on the Gear icon.
2. Under the Profile column, select Feedback.
3. Type in your comments or product suggestions in the box.
4. Select Next to submit.

Furthermore, you can track the feature requests through the QuickBooks Online Feature Requests website.

Meanwhile, if you want to send the complete transaction details to your customer, I have another option for you to follow, which is to send a paid invoice personally to your customer's email address. 

Here's how:

1. Click on the Customers & leads, then select Customers.
2. Select the customer you want to send the invoice.
3. Locate the paid transaction, then click Edit.
4. Click the Print and Download, then select the Save icon to download the file. 

You can also create and send statements to show customers summaries of their invoices, payments, credits, and balances.

Additionally, you can check this link to generate a sales report: Use reports to see your sales and inventory status. 

Don't hesitate to reach back if you need further assistance with sending receipts or any QuickBooks-related inquiries. The Community to help you and provide the support that you need. Have a great day!