I would like to remove the customer message (e.g Thank you) that appears on my invoices. Customise invoice does not help (it's blank but the message keep getting added.

Hello, nomfundo-naswend. 

Thanks for choosing QuickBooks in managing your business. I've tried some testing on my test company to see if there was a way to make amendments and remove the message that appears on the customer message every time you send an invoice. Yes! you can remove it by going to your Custom form styles. I'll show you how to do it:  

1. Click the Gear icon and select Custom form styles. 
2. Look for the invoice or sales receipt that you wanted to modify and select Edit. 
3. In the Emails section, Unchecked the Use greeting and delete the message in the Message to customer box. 
4. Press Done once finished. 

Make sure you set the New invoice as Make Default to reflect the changes made. 

If you're still getting the same issue, I recommend importing custom form styles for your sales template. This way, you can create a unique identity for each sales forms. 

Don't hesitate to drop a comment below if you have other questions. I'm more than happy to help. Take care!