I recognize how important it is for you to utilize a second phone number of the invoice header in QuickBooks Online (QBO). Let me share some information about the product limitation of this feature.
As a business owner, it's essential to add a phone number for your business. However, the invoice feature of QBO can only cater to one phone number in the header.
Despite this, we highly value your input, which can influence future updates. Therefore, we encourage you to share direct feedback with our product engineers.