How do I add RT0001 after my business number for printing on my invoices?

Good day, Lisa Milligan,

QuickBooks Self-Employed only lets you enter the 9-digit business number. You can add the extension number on the message section of the invoice. 

Here's how:

1. Click Create invoice.
2. Enter invoice details.
3. At the lower left side of the screen, enter your business number with the extension on the Message box.
4. Send or Save as draft the invoice.

Please let me know if there's anything else I can help you with.

When you customize the design of your invoice, you could add the business number inside the HEADER.  In the header (of the design template called 'Friendly'),  I put my company info, name, address, email, phone number, website address, and I added a full business number (ex. HST ..... RT0001) on a separate line at the bottom. That way, all the info related to my company or small proprietorship is gathered there. There might be other alternatives, but this option seems to work.

Thanks for your response!   However, I don't see the option to customize my invoice.   It would make more sense to put it in my company header, instead of the comments field on each invoice.   I consulted the help and it says under the 'gear' select 'my company' to customize forms, but I don't see this option.  Perhaps it is different for quickbooks self employed?   

Indeed, it might be different for Quickbooks Self Employed. This is one way to customize your invoice in Quickbooks Essentials :

Dashboard > Start Invoicing > Customize your invoices

see pic attached

Yes, it's different with QuickBooks Self-Employed, Lisa_Milligan.

As of the moment, you're unable to customize the invoice template. You'll want to follow MaryLurleenM's suggestion on where to enter an extension.

I will submit your concern to our management so they can pass this to our product developers for review. They might add the feature to edit an invoice template in our future updates.

If you have other concerns, you can always leave a comment below. Have a good day!