I acknowledge that it's essential to customize the delivery notes to leave a great impression on your customers, Chanchal.

When you create a sales transaction, such as an invoice, the number will appear when you print the delivery note if it has a digit assigned to it.

To reach your goal, I suggest removing the invoice number before printing the delivery note since QuickBooks Online currently does not offer an option to customize it.

Here's how: 

1. Hover over the Sales menu. Look for the invoice you want to print a delivery note.
2. Click Edit. Remove the invoice number.
3. Press the Print or Preview option below. 
4. Hit Print delivery note. 
    

You can always add the invoice number again if you wish to. 

While removing the "Invoice No" option isn't possible, I recommend submitting a feature request to our product engineers. You can also suggest adding an option to customize delivery notes based on your preferences.

Here's how to send a feature request:

1. Go to the Gear icon. Select Feedback.
2. Type in your feature request or recommendation in the description box.
3. Once done, click on Next.

For future reference, you can send your customer a statement to provide comprehensive details of their associated invoices, payments, and outstanding balances in QuickBooks Online.  

Removing the number before printing the delivery note, you can ensure that no invoice number is displayed. If further assistance is needed, feel free to reach out. Have a good one, Chanchal!