Why does the estimate email sent to customer say it is an invoice

Thanks for reaching out to us, treesplusltd.

Upon checking here on my end, there's an ongoing investigation (INV-100722) about the sent estimates that will show as an invoice in QuickBooks Online (QBO). With this, I recommend contacting our support they can add you to the affected user's list and you'll be notified via email once the update is available.

Here's how:

1. Sign in to your QuickBooks Online company.
2. Select Help (?).
3. Select either of these tabs:

• Assistant tab and select Talk to a human.
• Search tab and click on Contact Us to connect with a support expert.
  
  

As a workaround, consider downloading the estimate and sending it outside the QBO.

Moreover, I'm adding this article as your reference for personalizing your sales forms in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

As you send your estimates, rest assured that I'm always here to lend a helping hand. Should you need assistance with any other areas, feel welcome to drop me a comment below.