@Rohan Sharma  can you share some info on which screen is this toast error message popping up? What are you trying to do when this error pops up?

Normally the system should not allow you to have more than one customer address type as default.

@Rohan Sharma The method, Get_Default_Address_Db is in Invoice area. If you can explain what you are doing that would be helpful to troubleshoot.

we try to post customer inv via instant inv and custome recipt booking using mixed payment method

@Rohan Sharma did you check the customer addresses? Does it have more than one address as default for Document Address type?

Moved the post to Framework and  Experience as the subject is not related to on demand webinars