Thanks for reaching out to us. Allow me to help you with the sales receipts.
When you create a sales receipt in QuickBooks Online, you have an option to receive a copy of the email when you send it to your client. Follow these steps on how to set it up:
Go to the Gear icon and select Account and Settings.
From the Messages section, select Sales Receipt from the Sales form drop-down.
Check the Email me a copy at [company email] box.
Tap Save, then Done.
You'll want to make sure that the email address is correct. You can edit and update it from the Company section.
If you're sending it to a different email other than the company email, make sure that you enter the correct email address. Also, it's best to check the spam or junk folders.